I buy a lot of rivets from this place:
https://www.rivetsonline.com/rivets-en/blind-rivets-en/closed-end-blind-rivets.html
Your existing rivets are probably 3/16 dia., and depending on what type rivet setting tool you have you could use the 3/16 or 1/4 dia.. The 1/4" require the heavy duty setting tool, but the 3/16 can be set with the regular setting tool.
The aluminum rivet with the steel mandrel is the strongest. Just dab a bit of JB Weld over the mandrel hole after the rivet is set.
The closed end blind rivets form a water and vapor tight barrier when set.
I like to dab a bit of Loc-tite metal epoxy to the end of the rivet for extra security, JB Weld will work too.
This is a good video:
https://www.youtube.com/watch?v=L0MA1-5NXjs&feature=related
I'll kick back and wait for the blind rivet haters to chime in now. :roll: