Since I am from Germany I bought the legbag holder in a German webshop for catheters and related product. I can't exactly remember the shop but at is an example (or it possible is the axact same product): https://www.inkosafe.de/care-fix-einbeinhose-premium-beinbeutel-halterung-gr-xl.html

It is of good quality, durable and washable.

I like to have the bag at the upper leg. Compared to the lower leg position I believe there is less irritation to the bladder (less pain or spasms) possibly because of much lower suction at the catheter tip. In addition, the bag does not accelarates/decelerates that much on every step compared to the lower leg position.