I actually purchased (a while back; don't know if still available) just the quad-connective enclosure, and then can put whatever drive I want in it. Right now it's just a BD-ROM, but down the road (when the discs are affordable), I can swap in a burner...or whatever other optical storage device comes around.
I believe it was ~$90.
Not cheap, but to be able to hook it up to my old PC (eSata card added) or my Macbook Pro (which of course doesn't have a blu ray drive, and is also running eSata via an expresscard, but which I hoookup via Firewire 800) makes it a very worthwhile solution.