I am not sure if such a thing exists, but I am certain something exists which will function in the way I desire. It is simply a matter of finding it!
Frequently, I go for walks at night, and carrying a ring of keys is not ideal. I am looking to make a copy of my house key, and carry it in a velcro holster around my ankle. Ideally, the holster pouch would be just large enough to accomodate one house key, to cut down on weight and bulk. It would affix around an ankle using velcro straps. The pouch would have to have some sort of padding/reinforcement so the key edges do not cut through it.
Does anyone know of something like this?