*** Blick sells PMC and supplies in it's bigger stores. They have a location in Vegas, although you might call them and check to be sure they carry it in their store.
Blick Art Materuials
290 S Decatur Blvd
Las Vegas, NV 89107
(702) 368-0209
These guys are supposed to have art clay silver:
The Bead Metaler
602 Wilshire Blvd
Las Vegas, (NV) 89110
Good luck!