What I did at my old place was just have a loop of strong cord tied off around the towel rack, and clipped to that at my leisure.

Currently I have the strop clipped to a split ring, which has a loop of cord and a carabiner on the end of it. This way it's more versatile - I can clip it to things with the carabiner while travelling, or for larger things, I run the loop of cord around an object, and clip the carabiner to that. The loop can also be used to hang from door knobs on its own.