I use 2x2-sized coin flips. They store thick, chunky ancient coins no problems so should be able to handle the odd shape of a trachy. I own a couple of Byzantine scyphate coins and they sit quite happily in these flips.
The only problem I can see is fragility; if you've got a coin with a nasty crack or some other flaw that might split the coin into pieces if it gets even a little constant strain (such as it might experience in a flip in an album) then you'd have to use something else.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis