I checked my Amazon order history. The ones I bought (back in 2013) are no longer for sale, unfortunately.
There are, in my experience, 2 types of display cube - one is thin plastic and has a lid of some sort. The other is thick acrylic and splits in two pieces. The second one is what you want. You'll know which ones are like that because they will look seamless (because the 2 sections split right on the edges, so there is no visible lid).
Here's some I found on Amazon that explicitly state it is the kind that slide together:
I'd verify that you like the dimensions first though. They fit pretty much any mini-fig, but because they are square there is a fair bit of space around the figure. I had to stop using them because I wanted them in a display case, but I had too many figures and needed to shave some space.
The golf ball version is too small for figures, but perfect for making individual risers. I bought a whole case of those just for that purpose. They have square edges instead of the rounded ones you find on most risers that can cause figs to slip.