I don’t know of anybody selling silver rivets, but they are the
easiest thing in the world to make. Just take some heavy silver
wire and cut it a bit longer than the length that you need. Hold
a metal block on one side and hammer the other into the rounded
rivet head, then repeat for the other side.
Look up GOLD, SILVER, PLATINUM DEALER in the yellow pages.
Anyone there should have no trouble supplying you with whatever
size silver wire you need. Figure about 25% to 35% over market
price for wire. Hope this helps!