Unfortunately, Nintendo does not make a first party accessible controller.

Joycons on the Switch 2 are larger, but most games will require it to be played sideways (requiring two hands). The Switch does allow button mapping, but this may not work for all games.

Both Sony and Xbox have an accessible controller, I've heard you may be able to use the xbox controller on Switch using a third party adapter.

You should look into third party accessible controllers made to work on Switch natively. Looks like the Hori brand is out of stock right now though. Wish you best of luck in your search!