Christine and Cheryl will know far more than I do but I can recommend a couple of things.

Whey protein (a milk product without the fat and other less desirable things) is readily available in the health food or fitness aisle of the supermarket. Or in fitness stores.

Skim milk powder added to smoothies is also good.

I dislike most meats now, mainly because I can't chew them but also because I just don't fancy meat. I try to eat pulses and eggs to provide me with proteins from non-dairy sources.

I have a recipe cut out from the local newspaper for a peanut raisin smoothie with a soy milk base. The recipe is by the winner of Masterchef NZ so it might be more palatable than it sounds.