I know a guy that does upholstery, according to him it's not fun. Now I've seen guys do basic stuff for older boat seats and stuff, that seems not too bad. I wouldn't want to do a car seat that I want to look good though. Unless of course you're an experienced seamstress.. probably wouldn't be a stretch.
Depending how dedicated you are... and how desperate to find other companies that do it. There was a place out of Lexington, KY that I was always told did great work. (Can't remember how far a drive between Nashville and Lexington) Coach Craft or something like that. That was a number of years ago though.