You can rebuild them yourself - did mine not long back. There is a post about this on one of the other forums; it includes a few diagrams etc.
A fair bit of trial and error is needed when swapping around the tumblers (the small brass bits that follow the cuts in your key). There are only 4 different patterns of tumblers for door (cab, rear hatch, engine lid - if fitted) locks. Ignition barrell tumblers are slightly longer but still have 4 different patterns. Door Lock seem to use 8 out of the 9 slots (the centre one left empty. Ignition barells seem to use all 9 slots.
I got a few knackered old door locks from auto jumble as donors for spare tumblers. If you decide to give it a go yourself give me a shout and I'll dig out my left over spare tumblers for you.
FS 8)