I use a device at the fitness center where I work out called a Sanddunestepper. You stand and walk on it (holding onto something if you need to). It mimics lwalking on sand so it challenges your feet and legs and helps my balance. But my feet burn instead of are numb so I don’t know if it will help you or not. You can see it in line at Sanddunestepper.com and buy one. They cost around $250 plus shipping from CA where they are made.