You can buy a packaged door system and cut it to fit. The doors will have a significant overlap and will not open more than 25 inches. OR you could call a glazier. They will fabricate a custom door that will not cost much more. Most of the cost and material in a shower or tub door is tempered glass. You can get custom glass or take what is available at the store. The cost basis is not much different, but obviously a glazier will charge something for his time, and will probably install it. Doesn't cost anything to check.