I have been buying my stainless ARP 12-point bolts from Summit Racing but you can't buy individual ones so it can be very costly. They sell nuts individually, but not bolts. McMaster-Carr sells a limited selection of 12-point stainless bolts.
Last week I found this site that sells any ARP bolts you want, whether one, two, or a hundred. Prices aren't bad either. They also sell chrome grade 8 bolts and lots of other hardware. Select ARP in the lefthand menu bar.
http://www.allensfasteners.com/default.asp