My husband and I belonged to a 'Volksmarching' club in Germany, where they are much more casual about a lot of things. I had stepped off the trail to "cop a squat", and one my fellow hikers saw how much difficulty I had getting my left knee to work so I could get out of a squat. She called me off to one side and showed me "the device" she used. I was intrigued and she gave me the name of the "outdoor sports store" she had gotten hers at. I went at next opportunity and picked up a couple of them.
Shortly after I returned to the States, I saw them at one of the big US outdoor stores, but I think it was Gander Mountain, which has gone out of business. They were also nowhere as nice, or as thoughtfully designed as the ones I had.