The modelmakers' source
This is the scale plastic stock and model parts catalog used by architects, scratch-build modelers, railroad hobbyists and other miniature makers. They have EVERYTHING at various mini scales: I-beams, T-beams, H-beams, tubing, tiny plumbing fittings, stone and brick-patterned sheets, plastic sheet stock in every size, color and thickness. The next time you watch a sci-fi film and see a far-away shot of, say a mining colony on a lonely asteroid, you’re probably actually looking at a big chunk of the Plastruct product line. Their website is abominable; get their paper catalog.
To avoid gluing your model to your work surface, especially when working with a fast acting solvent cement like Bondene, we recommend you do all cementing on a sheet of polypropylene. Even better, purchase a few serving trays (cafeteria style) and cut the polypropylene sheet to snugly fit inside. This way, the sides will capture any spilled solvent cement before it spoils furniture, and you can use different trays for different in-progress projects