I'll have to see what we have locally. I know i had no luck finding anywhere selling RTV but that's not a shock lol.
I like to purchase sheets and also pre-cut strips and rods and/or tubing in both the squared and rounded versions.
You could also hit hardware stores for 'for sale' signs and the like. They come in many different thicknesses and are the same stuff! I always buy my plasticsat our local hardware, and save a bundle.