I haven't been able to go to the Muay Thai gym for a while, thanks to COVID. While I can practice Kata for my kempo stuff, I am itching to do some muay thai stuff and hit the heavy bag, which is obviously not possible now. I am doing shadow boxing, but it really want to hit the heavy bag. So here goes, what can I do? I'd buy a wave master, but they take too much space and too heavy to move around on a daily basis. What can I buy or build on my own?