The rivets I've seen that were used to attach those tags have a short knurl just below the round head that swages itself into the blind hole in the cast iron. A plain aluminum or brass rivet with a shank about 1/8" long will expand as it bottoms out in the hole well enough to hold the tag in place. It could also be attached with epoxy cement and fake rivets inserted and glued into the holes.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!