As tofu said, this would be the cheapest way.
I got mine from a SNES Clone Controller here:
http://www.gearbest.com/mice-keyboards/pp_261728.html
I salvaged one from it, so i still got 1 (for 2 buttons) left.
The shipping to UK will be much more than what you would have to pay at Gearbest,
so i think you should go the GB route first, but if you insist, i can take a look what shipping would be from DE to UK
and send you the other 2, but i think you should go with the new one, especially if you make a mistake so that you will have a backup.