From msbuck: << The only other suggestion, which is not a good one by any means - only as a last resort, is to swap out the entire latch with the updated ones that you can use the same key as the ignition. Very expensive alternative I would say...>>
True, *but* — There might be slightly less expense if the current touring-case locks fit your older cases. When I bought new touring cases at Bob's last year, I bought a pair of locks for them. The pair was keyed when installed (I think they were pre-keyed as a pair, but I'm not positive.) The pair wasn't cheap, but I don't remember the price being a killer, either. Of course, that solution requires putting up with the PITA factor of not keying the new locks to your present ignition lock, or (shudder) buying a complete new set — ignition, seat lock, and touring case locks.