Another vote for buying the appropriate shoes. See if you can find coupons, rewards, buy used, sell outgrown but in good condition, etc. It might help with the cost.
Alternatively, if the PT or other medical professional approves it, go the opposite direction and do bare feet/socks/soft moccasins that will protect the feet but otherwise are basically bare feet. Not knowing what the medical issue is that might not be appropriate, but if is ok it would be a lot cheaper.