Approximately 100 miles from the city is a shop in La Moille,Ill. that does good upholstery work. The name of the shop is Bennetts Upholstery. Good work and reasonably priced also.
What exactly are you looking for when you say custom? I see a few posts about inexpensive work in Illinois, but not near the Chicago area. So what you are saving on work you are burning in fuel and at $4 a gallon it may not be worth it. I can say if you are willing to drive the Custom Shop in Flanagan turns out some nice buids and he is a nice guy.
There are a few places local, Ogden trim and Top in Berwyn and Addison trim and top in Addison.