i worked for a van body repair/rebuilding place,where we used them when there was no access to the backside of the panel.they are strong and hold better than the pop type rivets.i used one in one of mine that popped on the bottom of my boat in a stringer.my neighbors boat has a few in them we lost the last trip out last year putting the boat on the trailer for the season.
where we get these were a rivet supply house.they specialize in just rivets and such.cant recall the name since i changed jobs,i still rivet but i dont do the ordering for them.if memory serves me correctly,mcmaster-carr had them,not sure on grainger,but fastenall carries them in there catalog.we buy them in 5lb- 20lb boxes,and they can get quite expensive,i was told $.05 each,so we used them sparingly.
if you have a trailer repair center near you,like the 48-53 ft variety,take a picture with you to show what you need.they might be able to hook you up with them.they come in 3 diffrent grip ranges,on the box there is a 4,6,8,4 being 1/4" thickness,and 3/8" and 1/2".for that area,i would go with a #4.that should hold tight.when we did the neighbors,he kind of is a little anal,so we dabbed a little sealant on the rivet,and in the hole then put them in.works great.for the area you are fixing,on the side like that,pop it in,drive the pin,forget about it,its not on the bottom like mine was.you might want to use a 1/4" one since the hole might be egged out a little.the 1/4" ones use a 17/64th bit.