I use the same method as Edseldave. I use #2 tap screws by 1/4" long.
I special ordered 500 of them when I decided to buy them. Better price for volume.
Matter of fact, Edseldave was the person that provided me with some useful tips.
The 1/4" long screws sometimes need to have the threaded end ground down or
otherwise you will have to drill a very deep hole for the tap screw.
I just grind the ends down on a bench grinder. And you can always grind more off if
necessary.
BYW I drill the pilot hole first and then drill out the rivet head with a larger drill bit.
Then you can go back and deepen the hole for the tap screw as required.
Word of caution: don't get in a hurry when doing this kind of stuff.
If you can find #2 tap screws by 3/16" long, they are shorter and work better.
Good luck with your efforts. This stuff is fun, too.
Cheers. Cobra