These racks are called "bottle shelves," and I got them from Daiso, the Japanese dollar store. They are meant as display shelves for nail polish bottles. However, their angle and size, and stackability make them perfect for display of coins! They cost $1.50 each, which does add up after you get like 12 of them, but I think it's a simple way to display coins en plein air. Plus, I like to pick up and hold coins and this makes it easier to do so.
Sorry, it's actually called a bottle stand. These go both sides up. I chose to use them with the shelf on the upper half instead of the lower half, but these things are fun and flexible.
I've looked everywhere in Western stores and Amazon but I have not find anything like these stands. The only bottle stands I can find outside of Daiso are these: Which do not have the slanted shelf; these might work with identically sized coins, but if they're different then they'll be at different levels.