I could not find these on Amazon's UK site, for the US:
https://www.amazon.com/dp/B081HX1HF4/
They're not inexpensive, but I find them to be the best, highest quality on the market. If I should need one I want something that will absolutely work, fast and best. The windlass is aluminum, and 'double' locks in place. Agree what bobbyOrrMan said about Israeli bandages. Less expensive, sterile, good for lesser-grade wounds where a tourniquet is maybe not necessary.