It's an old term, probably obsolete by now, but someone who sells fabric is called a mercer.
auctioner
A hatter
Ironmonger.
A hotdog vendor
A confectioner.
Draper
An agent or representative.
Daniel Studley.
clothier
Pottery barn sells some of their fabric in their catalog. You can call them and inquire which specific fabrics are available. I would think that people probably sell the fabric on eBay as well.
A confectioner is someone who makes and sells candies and sweets. A chocolatier is someone who specifically makes and sells chocolate.
locksmith