I'm looking into the suggestions, but also found two other toothbrushes from GUM.

One is called "Post-Operation" and it's incredibly soft. So soft I have to brush gently so I don't bottom out the brush. I wish I had had one of these post treatment. But too soft for me now.

The other is called "Sensitive Care." It's softer than the Biotene ultra soft brush I have. I wish it were just a tad softer, but it's the best I've tried so far for the level I'm at now.

I never found these before when I was looking for brushes using search engines. I only found them because I looked around the Gum website.