I’ve popped up some C4 S6 parts on eBay.
Audi S6 (C4) 4-speed Automatic Gearbox Controller 4AO927156L
https://www.ebay.co.uk/itm/303663052796
Audi S6 (C4) 1994 ABS-EDS control module 4D0907379J
https://www.ebay.co.uk/itm/303663048381
Audi S6 1994 (C4) Central Air Vents 4A1820951.
https://www.ebay.co.uk/itm/303663041146
Audi S6 1994 Ashtray 4A2857951A RL
https://www.ebay.co.uk/itm/303663031577
Audi S6 (C4) 4-speed Automatic Gearbox Controller 4AO927156L
https://www.ebay.co.uk/itm/303663052796
Audi S6 (C4) 1994 ABS-EDS control module 4D0907379J
https://www.ebay.co.uk/itm/303663048381
Audi S6 1994 (C4) Central Air Vents 4A1820951.
https://www.ebay.co.uk/itm/303663041146
Audi S6 1994 Ashtray 4A2857951A RL
https://www.ebay.co.uk/itm/303663031577