In pursuit of various diy projects, I often need materials, components or items which are not regularly carried in stores. For example, for a small diy vacuum chamber which I would like to build, I need a 1-2 foot length of 10+" diameter PVC pipe. I know that I can buy 8-10 feet of such pipe at a local big box store, but I imagine that people who regularly use that product, must occasionally have to trim it to length, leaving the part I want garbage-bound.
So what material acquisition life hacks can you offer?
Where do you look for those things which can't be found in (or afforded from) standard retail stores?