Cut out the middle man by going direct to the manufacturer. Makers of craft supplies (and practically anything else made by companies) can be found through the Thomas Register. It lists most major manufacturers by product. Your library should have a copy in the reference section or see: http://thomasnet.com.
Wholesale suppliers sometimes advertise in publications related to your craft or in the craft show guide magazines. Note that most manufacturers require a resale number and may only sell to you if they think you are a dealer or a store. Some craft supply wholesalers will sell to professional crafters, some will not.
The trick is to contact manufacturers as if you were already in business as a retail store. Many wholesalers will be satisfied with seeing your sales tax ID, business stationery, business cards, and the names of a couple of other major suppliers you buy from. However, some might ask for photos of your ‘store front.’
Don’t be discouraged if a big supplier turns you down. Just keep trying until you’ve managed to open accounts with any suppliers who will give you thirty days terms (net 30) to pay your bills.
If your business alone does not generate enough sales to justify buying supplies in large quantities from wholesalers, join together with friends or friendly competitors in a similar position to make a big purchase. See if fellow crafters or guild members can help make up the remainder of the order. Networking this way helps everyone.
This article describes one of seven money-saving ideas excerpted from the chapter “How to Slash Material Costs” from the book How to Price Crafts and Things You Make to Sell