I snapped the key off in mine once
If it's one of the old ones (I think E36 type) then you can just lever the catch off with a screwdriver. A triumph mechanic showed me that...
It doesn't damage the catch at all and you can then just unscrew the lock from the inside of the case.
Givi sell new locks/keys I think mine cost about £20 from local dealer.
I got rid of mine soon after though, they're stupidly easy to break in to...
As to the original question, take it to local givi dealer, they should hopefully know what to do