Hank,
You are talking to a guy that used his brains, looks and communication skills everyday in my career before cancer...and you're also talking to a guy that lossed it all due to the effects that cancer and treatment had on both my looks, ability to communicate and in some ways my thinking and reasoning abilities. I can relate.
As Christine has pointed out, you need to discuss things with your Dr, my opinion your MO is the best option as generally the General Practitioning DR's are not equipped to give educated advice on the matter to cancer patients. What I've found is that I've had to look for answers on my own and run them by my medical team and then see what works for me as everyone is different. Being unique biological entities does have its hang ups like that.
Now the way I looked at it when I knew I had an issue with memory and cognitive abilities was I needed to find the "cause" of the issues as it's always the easy answer for Dr's to give you scripts then to get to the root of the cause. In my opinion, treat the cause not the symptoms as when you start adding different drugs to the mix you are going to complicate the matter by the side effects caused by those drugs and they might not even be necessary.
We can just chalk up the cause as "chemobrain" which will give us these symptoms (taken from the Mayo Clinic's Site):
Being unusually disorganized
Confusion
Difficulty concentrating
Difficulty finding the right word
Difficulty learning new skills
Difficulty multitasking
Fatigue
Feeling of mental fogginess
Short attention span
Short-term memory problems
Taking longer than usual to complete routine tasks
Trouble with verbal memory, such as remembering a conversation Trouble with visual memory, such as recalling an image or list of words
Now what's not known about "Chemobrain" is if it's actually caused by the reaction to Chemo itself or from the other factors that go along with the disease...the emotional and physiological responses to treatment and or drugs etc... So what I did was narrow down my symptoms and see what could possibly cause each and then look for the solutions based on that information.
What I found was a mixed bag. I had low testosterone due to both radiation damage and long term opiate use, which will cause similar symptoms, as well as PTSD (post tramatic stress disorder) which will do the same. So it doesn't have to be just "chemobrain" it can be of slew of other issues especially if you are using some prescribed medications, opiates and benzodiazepines (both of which are commonly scripted to us cancer patients, I was on both) will also have an effect on cognitive function.
My approach was to cut out the chemical culprits, opiates and benzos for me (a long term effect of benzos is actually cognitive impairment), and then treat the low testosterone and PTSD. I also started reading on how to help my cognitive abilities, there is always a way to sharpen a knife no matter how dull it is to start with you know

What I've done:
Exercise and nutrition: they do a body good...and the mind. Strong body strong mind. Google exercise and cognitive abilities and do some homework. Nutrition and exercise play a BIG role in how the mind works so it's always a good idea to sharpen up there, at least in my "humble" opinion. (I don't think I can ever be considered humble!!!)
Supplements: There are natural herbs and supplements used by different cultures throughout history that recent studies have shown to be effective in boosting memory and brain functions. I'm going to give you a list and do some homework. Ask your MO about the ones that you think may make sense and then start experimenting.
Acetyl L-Carnitine
Alpha GPC
ATP (Adenosine Triphosphate)
Carnosine
DMAE
L-Glutamine
Phospatidyl Serine
Vinpocetine
the B's! (B3, B6, B12)
Fish Oil(it's good for more then just your heart)
Kola Nut (this stuff is awesome if you are a caffiene junky...say good bye to espresso if you buy the extract)
Ginseng (I use korean)
There are "scores" of magic supplements out there but I've listed these handful of supplements that actually have studies backing their effectiveness. Notice I didn't list Ginko-biloba as the studies have been inconclusive. The more you read into these they may make sense for your situation.
As a former wrestler I used supplements to keep me going when I couldn't use food for nutrition. When used in conjunction with diet and exercise it's a powerful thing

As a 37 year old cancer survivor who's body was devastated by tx and surgery I can run at pretty high pace now and I look and feel amazing. My mind's pretty sharp as well, especially considering the dull of utensil I started with.
Memory games, reading...you know, using the noggin. Usually exercising the mind will help sharpen it.
Lowering stress as stress will impair thinking as well (exercise, yoga, meditation, sex, etc...)
Sex...yes, sex will help you think believe it or not. Google it if you don't believe me
Counseling: I started counseling to help with the PTSD...cancer is very tramatic, both personally and to those around you. Counseling allowed me to work through some of the feelings and emotions I was going through and to help those around me (my wife and kids) cope with the experience. It's given me the tools to help myself and an outlet for my frustrations and fears.
Anyway I know this is a short novel, I apologize. I just wanted to give you food for thought as I'm no expert, just a fellow survivor trying to navigate my way through this crazy journey. Hopefully there is something useful in this reply.
Good luck
Eric