"What's a good source for..."
While I personally buy a lot of my supplies retail (insert grumble noises) a good Google search is the place to start online for wholesale goods. The difficulty I find with buying wholesale is that the quantity you need to buy can be extremely high. Especially when you're testing out a new product or are just getting started. Perhaps you only buy your packaging supplies and most used materials like chain, glue, or yarn in bulk in the beginning. Back to the search for a good source - you may have to try several different keywords and peek at several sites before you find something that fits your needs. It's also good to note that there are several great supply sellers on Etsy. Whatever it is you're looking for, keep searching. If you're able, keep your design flexible so you can adapt it and use the supplies you're able to find and afford. There must be someone more supply savvy than I that can offer advice. Care to share your wisdom?