I got a higher backed, well contoured, and Padded chair that some of the quilting shops are selling. I have a badly damaged back and no chair allowed me to sit for more than a few minutes to sew until I got this chair. Expensive-yes but worth every penny. They periodcially run specials at some quilt shops.
No it's not custom, but it might be an option.
NOTE: mine has a higher back, they sell some with shorter backs but that wouldn't have been as good for my back. Also if you find a chair you think is comphy, don't just sit in it for five minutes not sewing. Use a machine at a store or take your own, sit in that chair and sew for 30 minutes or longer just to be sure that chair really remains comphy for you (as if you were home sewing). Also my chair raises and lowers really easily-huge plus.
Good luck,
Kat