If the local Ace/Home Depot doesn't have what you need, I just looked at the MicroFasteners.com site and they have alloy socket head M6x50 or 60mm $2.90 for 10 bolts. I couldn't find anything in nylon.

Like Ram3500 suggested, I'd consider refitting the hold down blocks with 1/4x20 threads, and using nylon socket head bolts. I think you can get 50 of the 2" long bolts from MicroFasteners for around $3.50. You could use 1/4" blind nuts, or fill in the old holes with an epoxy/microballon mix and re-drill/re-tap the hold down blocks for SAE sizes.

Fred