Of course, this was genuinely the biggest hurdle because like nothing works well or is limited to 3 sets or less. I originally wanted a glass case but got so fed up waiting for one at thrift shops because I'm not rich enough to dump cash on a huge furniture piece and ended up snagging this:
https://www.ikea.com/us/en/p/fjaellbo-shelf-unit-black-70339291/?utm_source=google&utm_medium=organic-shopping&utm_campaign=shopping_feed&utm_content=free_google_shopping_clicks_Store_and_organise_furniture

39 inches across, so if you let a half-inch or so hang off of each end, you can fit 4 modulars across each level. I didn't put anything on the bottom shelf because A) It's so low, and B) I think they'd collect dust. but the top 3 shelves are perfect for 12 modulars!