I have a 6 year old Tilite ZR and the back is wearing through. Anyone know where I can get a replacement?

Obviously I don't want to go through a local DME provider, because I'll need the replacement this decade.

Doesn't look like I can buy them on sportaid, there are a bunch of other brands, but I have no idea how well they will work, and I really like the back that came with my chair.

Is there a way to buy parts/upholstry directly from TiLite?