It's not available until May 4th, everywhere I've found it:
Bloody crying shame that it doesn't protect the lens, though. I'm guessing that's because it won't fit in the speaker dock if the lens has anything added around it. (The clear / flat purple cases lack holes for the pogo pins, and hence can't be used with the speaker dock). If that's the case, whomever designed the dock should be shot.
I'm also curious whether these slim cases work with the car dock. I'm guessing not, because it's a fairly tight fit even without a cover.
Seriously, HTC. Fire whomever designed the accessories. There's no reason the lot couldn't have been designed so that the car and speaker docks worked with or without the cases, and that the cases could've provided lens protection. As-is, every single accessory seems to be a compromise somehow. :(