Olympic "bulb tite" shaveable rivets are available from several internet sellers. I've been buying mine from Vintage Trailer Supply. I also purchased the rivet removal drill tool, and the rivet shaver tool (expensive) from them.
The Airstream standard rivet is 5/32 diameter, that's the size Olympic you want.
1/8" pop rivets are available lots of places, including your hardware store. I buy the ones painted white on the head for interior work. You will need a rivet tool for those too, also available at the hardware store.