I did not know this format was a thing, and in fact I only came across it when browsing the Chamonix website, but apparently they sell 8x8 film holders. These are just 8x10 holders with an 8x8 film opening. Apparently Ilford will make it during their ULF sale, or you can cut the film down. I couldn't resist, so I ordered a couple holders.

In the process, I ordered 2 5x7 holders that will expose a 5x5 square! That will be great for enlarging.

Like I said, hip to be square.