I've used the UM nylon and the Aker leather ones. Mika's makes a vest holster, too. I've had the same thoughts as you about adapting an existing kydex holster. My thinking was adding velcro to the back of a CCC VersaClip and capturing the vest strap with a long PTD loop from a Flashbang (bra) holster, but I haven't cobbled it together yet.