hey jack, being new to this hobby and trying to find affordable parts, HARDWARE, etc... can be the hardest thing about it I think.
"McMaster-carr.com" is a supplier that I think is one of the best for prices!! they got tons of things you probably need.... screws, bolts, nuts, metal, the list goes on and on. lol
anyways...
here is a link for the correct most comment MM bolt used (you can get any length) but this link shows you an example....
a 100 count bag for only $4.00...
http://www.mcmaster.com/#92095a183/=ymc37m
hope this helps ya...
shaun,
tampa fl