It's been a long time since I last posted anything. But life kind of got in the way

The S4 has been treating me fine, it's been serviced at Audi Centre Cape Town regularly. About two weeks ago I got the dreaded....."Gearbox Malfunction you may continue driving"....then last week I lost reverse, 2nd, 4th and 6th.
Dealer quoted me £10K to replace and install new gearbox/transmission.
My question where can I source a new gearbox (might even consider reconditioned or used) from in the UK or Europe?
Your help guidance and insight will be greatly appreciated.
Herschel