I work in a small company that makes parts for several RC companies as well as our own line of RC parts. Most of the screws and other items you need are available from http://minibolt.com/ Don't be fooled by their web site they will do their best to get you the bolts you need. You should expect to order a box of each size you need. (50 or 100ea) We buy most of our fasteners in 5 to 10 K numbers and get them from ndufast's Victoria, BC store. Gerry, the manager is very helpful and when we were only buy a few hundred at a time he still treated us like valued customers. http://indufast.com
As for making the parts, prototypes are more expensive than production runs so you should look for as many parts as you can find from production RCs. We always look hard at other manufacturers parts list first before we think about making our own parts. Even with a good shop and cheap labour (read FREE labour) from the owners it costs more to make your own than buy a ready made part for your prototype.
That said, we would like to quote on any aluminium parts you need, especially milled parts. If you need formed or cast parts try to redesign your prototype to use bolt together assemblies. Once you have your design down you can spend the money on more complicated programing and molds.