I replaced a tourpak latch using stainless bolts and nuts. I don't know the size but they were a perfect match to the size of the tourpak holes. They were a standard size at the local hardware store. Even with no Locktite, they stayed on forever. Like you said, the nuts were hidden under the rubber gasket. There was no interference and it was much handier than beating rivets into place. The replacement latch included rivets but I didn't have the tool to install them.

(EDIT From the above posts, HD now include bolts. Back when I repaired the '89, rivets were supplied.)