www.spiderholster.com
Was this what you saw? It looks alright and sturdy enough, but I don't think you can use it at the same time as Arca-Swiss plates for tripods. (unless you take the spider plate, and attach an A-S clamp, so you can easily swap between hand, belt, and tripod)

edit, hmmm, ok, just realised how old this post was. Oh well, could be useful to anyone searching in future...