I think there is definitely a market for clothing for the physically impaired/handicapped/limited mobility. Tapping into that market will take work. I would think that making a few garments for your wife and taking some great photos and making up a flyer is where I'd start. Then show the folks at the Doctor's office, Hospital, Church or wherever you can what you've made and tell them how it improves her life. The get permission to leave flyers and see if you can get them to refer customers to you. If you can get a few people excited about your wares, word of mouth is cheap and effective advertising. Just what came to me reading your post.