A few hundred years late, and a bit on the expensive side compared to its competition:
https://www.google.com/search?q=strap+on+milking+stool&tbm=i...
I built one of these for backpacking trips for a little less than $5 for a wooden disk, a couple plumbing bits and a clip belt. Silly looking when you're walking around with it, but infinitely better than sitting on a wet log next to the campfire.