I don't know about the part number, but I picked up the belt drive conversion at Hobby People today. It appeared to be the only one in the Pasadena store.
Lots of parts including new side frames, tail boom, bearings, etc. are included-more than I thought there would be. I have not performed the surgery yet as I just completed a rebuild with the last of my V1 parts (of course, I have a V1 new in the box as a complete set of spares too!
When I install the belt upgrade, I will post the results, if no one else does it first.