The GIVI/Kappa keys, or at least the the standard old type keys are stamped with a 3 digit code.
If you have the code they can be cut, but you have to have the patterns for the keys.
When one of the lads locked his keys in his topbox in the dealers we used the tub of spare keys and all the keys from the display boxes and found one that was close enough to the original to open the box.
You can get replacement lock barrel and keys sets and keyed alike packs of 1, 2, 3 and 5 barrel/key sets.
I bought a set of 5, I wanted 6 but they don't do more than 5 - for my 3 pannier sets, but at least 2 sets of panniers are the same keys now and I was going to key our top boxes alike, but the security key barrels are a fair bit more.