Heloguy, Welcome to iRV2.
I'd recommend taking it to a local sheet metal shop...or drat, a RV shop. It really shouldn't take more that a couple of minutes to install two rivets.
To properly install 'pop' rivets, the diameter and grip length need to be known. Also, the rivet tail after the installation, needs to be of a length that does not interfere with any structure that may be behind and still maintain a 1&1/2 D ratio(that's 1&1/2 times in length to the diameter of the rivet).
There are different sheer and tension loads associated with different types of rivets and applications. Depending where on the slide the rivets are missing, there may be loads applied to those rivets that might call for some evaluation as to the proper strength of the rivet...I don't know. I will say that rivets usually don't go missing without a reason and maybe should be looked at by a professional.
Jan and Bob