I'm pretty sure Olympic is a brand name of rivet with some patents that may or may not be active. In any case, you have a Fastenal store in Gilbert that will stock all the rivets you need, they just won't be "Olympic" brand, but will hold just fine. Others will have other opinions.
If you do a search for rivets on this forum, you'll eventually find the sizes you need. I've found that 1/8"x1/4", 1/8 x 1/2, 3/16"x1/4", 3/16"x1/2", and a 3/16"x1/4" with a wide flange have covered everything I need.
Also, if you are using any of these on the exterior, you'll need to seal them with a polyurathene caulk - they leak.