As a follow up since I quickly typed out my reply last night,
If it's a 3/16" hole and you need to buy fasteners anyway, I would highly recommend just getting a dimpled (2xxx series) aluminum solid rivet and finding an air hammer or someone who can set them. The closed end pop rivets end up the same cost each, stainless screws with nuts will as well. On my build I had stainless closed ends on hand already but I know I may have to change them if leaks form. Screws with serrated lock nuts should work well, but they also don't swell to fill the hole, so they rely on the sealant to fill the voids, the rivets are technically more water tight on their own. I did use stainless button heads where I was installing 1/4", as my air hammer couldn't get the rivets to buck, even at full power...
When I ran out of 5200, I used pc7 epoxy putty as sealant on the screws. It is a glass reinforced putty, plus some other stuff, very hard and reasonably impact resistant, incredibly difficult to remove from my mixing trays and tools. These were permanent installs though. I'm relying on the epoxy to help prevent loosening, as well as high torque. Just as another option. Don't use it for rivets though, it's a bit thick and may prevent proper tightening.