I have seen the identical circuit described elsewhere, but 2N2222 vs BC847b for the 4 NPN's, 2N3906 vs BC856b for the 2 PNP's, 1N914 vs 1N4148 diodes, and a 1N751A 5.1V zener diode. All the 2N and 1N semiconductors, as well as the 4 terminal mini phone jack are available from Mouser ( http://www.mouser.com/
), and no doubt elsewhere too, perhaps even Radio<cough!>Shack (need a cell phone w/ those electrical thingies...?).
There is a schematic for a two transistor version floating around too, fewer components, but reported to give some people problems getting it to work.
Believe the same 6 transistor cable also works w/ the VX-150, VX-5 and FT-60 also w/ Kenwood's TH-71a etc. (but a differant phone jack for the KW's?)