It's this one on eBay:
BMW E30 E34 E36 E39 Z3 X5 1982-2001 Sockets Oil Service Reset Tool 20 Pin
http://www.ebay.co.uk/itm/4007114895...%3AMEBIDX%3AIT
For my MY2000 Z3- I've also got an OBD2 service code reader for that 20 pin socket under the bonnet. I've never used the D-connector under the dash.