I'm not sure if HD or Cdn Tire is a good idea. The bolts that come with bindings seem to be hardened steel -- pretty high quality. If I slip with the screwdriver I haven't rounded the slots yet. With the soft metal crud that HD and such sell you, you can sneeze on it and strip the head.
HD should have it in metric m6 size I believe. I got screws at a local place because it was higher quality. The hard part is I cant find washers. I just bought two sets of screws from sports chalet for 6 bucks each though.
Binding screws are sold in different lengths too, so make sure you get the right ones. If the ones that came with your bindings are correct, take one with you to compare to the new ones before you buy.
16 Gnu Swallow Tail Carver . 16 NS West . 15 NS Snowtrooper BIA
16 Burton Genesis X . 15 Now Drive
16 Flow Talon . 14 Flow Hylite