Rivets Size (Tri-grip)

What is the grip lenght of the rivets ues on the Hobie Kayaks. The ones that are being sold at the kayak stores are the long rivets. I was using some to attach a few additional eye-lets. But when they popped there was at least 1 inch of metal that needed to be cut off. I want to get right size rivets so that when the rivet pops; it seats perfectly. Can anyone tell me the size and where can I purchase them? Of course I'm looking for water tight rivets. (the ones with the rubber washers' already installed.)