Quantum-
I replaced several rivets on my coach's slides. One or two were large-flange rivets; I eventually found a source: Albany County Fasteners (link
here).
I bought a couple hundred rivets and a pneumatic rivet gun from them when I repaired the beltrail in 2020. That was a lot of work.
As mentioned, you'll need to know (as closely as possible) the rivet length, diameter, head size and material.
Notes:
1) Common RV rivet materials are aluminum and stainless steel.
2) A hand rivet tool you buy at the box store or auto parts store will usually work with aluminum rivets up to 3/16" diameter. The same tool may work with stainless steel rivets up to 1/8" diameter, or maybe not. To secure stainless steel rivets it's better to use a compound (two-arm) hand tool (similar to
this one) or a pneumatic tool.
3) I learned from Albany County Fasteners that each rivet size has an optimum drill bit size to make the hole. For instance, a 3/16" uses a #11 drill bit. In your case, if you're replacing a rivet that doesn't matter as much.
4) A rivet can conduct water from outside to inside. Be sure to apply caulk in the rivet hole and the backside of the head, and then apply caulk over the hole in the center of the rivet after you've put it in place. For the former I used white polyurethane caulk and for the latter either the same (if in an area that's not visible) or ProFlex RV clear (if in a visible area). If on a roof, completely cover the rivet with Dicor self-leveling lap sealant.
5) Rivet removal is tricky. If you're not careful you can damage the surrounding surface. The easiest method for aluminum rivets is to use a punch to drive the rivet center out the back of the rivet. If the rivet is much longer than it needed to be this won't work well. The next method is to drill out the center of the rivet flange or head. If you do that too aggressively the drill will grab the rivet and spin it, and that makes further drilling almost impossible. When I drill, I try to apply light pressure and slowly increase the drill size. You might also try putting a strong-grip duct tape over the rivet head before drilling, to reduce spinning. For stainless steel rivets you may have to use a grinder to remove the head- with a lot of chance to damage the surrounding surface. In all cases, proceed slowly.
6) For blind holes I have used a probe/pick or piece of wire to determine material thickness so I can select the correct rivet length.
7) Have some touch-up paint ready.
8) While I did not use them for slide repairs, I have used tri-fold or "Oscar" rivets in places where I needed extra strength in a blind rivet. A link to them at Albany County Fasteners is
here.
9) Lastly, before doing any rivet work check what's behind or under the rivet, if you can. The piece you drive out of the middle will fall somewhere (to lodge or rattle), and the drilling you do may hit something important, such as cabinetry, ceiling or wiring. Do the slide work with the slide all the way out.