Small hardware stores are the best places to find stuff that those big box "hardware" stores do not sell.

I have two Ace Hardware stores near me. One sells stuff like screen and small bits of metal tube. Can't find that anywhere else. They also sell cork and other odd bits.

The other sells everything dremel. Even off brand dremel stuff. They also sell sandpaper for $.99 a sheet. They also have the largest plumbing department anywhere with a better and more comprehensive shelf stock. And if you need a bolt, screw, washer, or any other type of fastener. They will have it or be able to get it.

Patronize your local small hardware shops. These guys know what they are selling and can help with your project.