I haven't seen anything yet.
I have a cheap "universal" (it's a lie!) PDA car mount which, with some strategic paper wadding, is an almost-perfect mount for my N810, and from the looks of it will probably work for the Epic as well, but only if mounted horizontally.
rufflez really has the right idea, IMHO. It's hard to find a perfect mount for your specific needs, but it's possible to combine a bunch of really cheap bits into something workable, so I'm not too concerned about official accessories.