It's an old term, probably obsolete by now, but someone who sells fabric is called a mercer.
auctioner
Draper
Ironmonger.
A hatter
A hotdog vendor
A confectioner.
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.
An agent or representative.
Daniel Studley.
clothier
AllenHeartFabric.com sells wholesale Loralie designer fabric by the yard and bolt. The more fabric someone buys, the less the cost. Buying by the bolt (12 yrds) is the best price compared to other fabric shops that sell the Loralie fabric.
A confectioner is someone who makes and sells candies and sweets. A chocolatier is someone who specifically makes and sells chocolate.