I think you can use standard v-brake cartridge pads. See this Nashbar product, which I believe is the Oryx rebranded. Even if it's not, it's the same shape. It comes with cartridge pads, and the replacement pads are v-brake inserts:
http://www.nashbar.com/profile.cfm?c...eid=&pagename=
If the link doesn't work, on the Nashbar site, search for "deluxe cantilever"