Ran into the same thing with a beat up DP-1 finder last year and the foam was crumbling into the prism housing. Grabbed a sheet of craft foam from the kid's art bin as a quick fix and it turned gummy within a month from humidity. Ordered the real stuff from a camera shop after that and it cut clean and stayed put, lesson learned the slow way.

Man, I feel this so hard, I did the exact same thing with my first pothos and felt like a total plant killer. North windows are basically a death sentence in winter, that "low light" tag should come with a giant warning label.

Seven year olds are a tough crowd for real jokes, just so you know. At that age they mostly laugh at potty stuff and anything that happens to their siblings. Your best material might just need a few more years to land.