sorry, I thought you were on about a g40 gearbox for some reason (I clearly didn't read the title of the post properly!).
But still, what I said applies. You can try VW but it'll be ££££££, I'd still give them a call to find out. 2nd hand is best bet but as I think you already know, those gearboxes commonly fail so finding a 2nd hand one might be difficult. Is there a similar one you can fit such as from an AFH engine 6n perhaps?