I haven't experienced a problem with footwear myself. One thing you could try are the "tone up" or "shape up" trainers made by Sketchers or Nike.

These are the one with the curved sole but are supposed the help with balance and posture. I did see one which had "micro instability" pads in them to promote balance.

I am sure they will be a bit extreme to start with but may work well if you persevere with them.