Quoted from Freeplay40:

As info, the rivet type is called a semi-tubular oval head rivet. The standard rivet is 1/8" in diameter, however as Bryan_Kelly says, the length of the rivet is the key. I've done 1000's of rivet on ramps. I use a rivet press and I also use a hand held rivet die (support the head of the rivet then hammer the die to roll over the rivet)
The hand rivet tool can be used for almost all riveting and is available at Hanson Rivets for $25 (Item #HT174). You can also purchase rivets at Hanson's as well. If I had to guess, I would think the length rivet you would need is either 7/32" or 1/4" (they sell them in increments of 1/32"). Not sure if there is a minimum order on rivets from Hanson's as I order in lots of 100.
There is a video of me using the hand held rivet roll over tool at the top of this page...
https://pinside.com/pinball/forum/topic/swords-of-fury-custom-ramps/page/8