I’ve made this stein using a bench top liquid nitrogen dewar flask. I’ve found dewars still holding good vacuum after 30 years. This is, for all intents and purposes, the very best thermos you’re ever going to find. It is quite common to fill these with liquid nitrogen, let it sit on the lab bench, and when you come back three days later there will still be liquid nitrogen in it.
Now imagine what it can do for beer.