I know this sounds like a big deal, but people who know what they are doing can make bumps stocks using rubber bands.
I’ve seen people empty an AK mag in seconds using their index finger and proper handling of the weapon. You sort of pull the weapon into the finger, it fires, recoil resets the trigger group, you’re pulling the weapon back onto the finger, it all happens fast. It isn’t accurate, but it can be done.
The BATF a few years ago decided that shoelaces were machine gun “parts”.
Thumb and a belt loop... With practice... Don’t even need that.