Buffalo has DVSM-D5812IU2 based on LG GSA-4120B on its Japanese website. DVSM-D5812FB is the internal version of this drive. Both will start appearing in Japan soon.
Since IO DATA's DVD+R DL drive based on NEC ND-2510A is selling for a little over 15,000 Yen, I can expect DVSM-D5812IU2 to be about from 16,000 to 18,000 Yen.
I am using a Buffalo USB/1394 drive based on Sony DRU-500AX right now connected to Dell Latitude D800's IEEE 1394a port. It's very slow: up to 4x speed.