I have a NEC ND-2500A in an external enclosure. It's working perfectly for me. Even the firmware-updater (for windows) recognizes the drive and is able to flash it correctly.
I can't recommend any specific enclosure, since I just re-used the one that came with my 'old' USB2.0 AOpen 52x cd writer. I simply put the NEC in it, but it doesn't fit entirely, so the case is rather instable, but tht doesn't matter much to me since I don't usually move it.