I know you already have everything, but i use the ones from napa, plastic riviets part #770-2871 - it's a twenty piece pack for $5. And a plastic rivet setter from napa part # 770-2864 it runs just shy of $20.
I'll keep that in mind next time. I just replaced my leaking exhaust manifold and bought the rivets from the dealer ($4 ea) and discovered my rivet gun wasn't big enough. I ended up pulling with vice grips and pushing with a screw driver, it worked, but obviously not ideal.