RE: Do you get your materials local? Where?
Im using 1/2" foam board for my latest project, and to make wings, the Home Depot here has 3" foam sheets. The door skins they have is a good substitution for lite ply, and They should also have birch plywood in small sizes that i use for firewalls. For balsa and spuce sticks, I go to the LHS, but if you want lots, I would order it online. The choroplast stuff, I havent found yet.
On my plane, for the fuse, im cutting the general shape from foam, and using fiberglass (automotive stuff cause its cheap and readily available) over top of it. I use wood glue to hold the FG down. So far its working pretty good, and the weight looks good too. Once im done the build, I will post finished pics and the final weight of the airframe empty, and with gear installed.
Some times you have to think outside the box