I recall those stick on reminders but don't know if they are still made.
My bigger problem is using unboxed film and not having a box end to stick in my M645 or 35mm cameras. I use a box end from another box, and if it's a different type I write the type on the back and insert it back side out. I find I always (well, pretty much) remember what's in my TLR because I only have one TLR and it doesn't of course have interchangeable backs. I have a terrible time remembering what's in which 645 back (because they look identical) or what film I put in which 35mm body without those things.