I bought this on Ali Express... like you I have no pin 7 and 17 on the gateway connector of my TDI S. I have already replaced the mid gateway with a high, Jack from Poland did all the hard work remotely. My T17d looks just like yours as well, no extended can bus wiring.
The little thing I bought on Ali means I don't have to wire into T17d at all but I may run wiring down there to make any future mods that require extended can easier. I may order these repair wires, info copy/pasted from one of Golfdave's awesome DIY threads...
If you want to wire via the TIUL T17d connector when you will also require:-
000 979 034 E, (A05 wire set), 1.5mm pin, 0.5mm wire, female side for TIUL T17d connector (4F0 972 483) £14.08 (x1)
000 979 035 E, (A05 wire set), 1.5mm pin, 0.5mm wire, male side for TIUL T17d connector (4F0 972 575) £9.29 (x1)
Good thing is each repair wire has 2 pins, one on each end, so you only have to order one of each wire to get both can lines at T17d. I have no intention of selling my car, and even if I did I wouldn't un-retrofit anything except my seats... but the little gateway extension dongle is a clean way to add can extended and means you don't have to muck with any existing harnesses... you just have to wait a month for it to arrive, haha.