FYI, pop rivets are the same rivets you used to fasten the holster to the belt, and CAP rivets are this kind of rivets:
http://www.whitearmor.net/forum/tutorials/article/19-how-to-install-cap-rivets-video/
But when i look at the materials used for your strapping system, it's really looking perfect, so it would be kind of the surprise if you'd have mistaken yourself regarding the ammo knee belt rivets. Maybe it's just the picture shown which is misleading.
But once again, Congratulation