It is possible to remove the lock tumblers, by depressing a small pin, but I think you need the key inserted to do this. Maybe a locksmith can do this without the key and he/she might possibly have the correct tumblers. The entire lock and shaft are available from many aftermarket Volvo parts suppliers, including the trunk lock (if that's also required). Here's the typical price you'll have to pay, with part numbers:

663804 Lock set left, right and trunk 120/130 set $86.95

655800 Lock cylinder left hand side with 2 keys RH each $36.82
655802 Lock cylinder right hand side with 2 keys LH each $36.82
666229 Lock cylinder trunk 120/130 each $53.70

The procedure to replace these is quite simple and since you'll have the door panel off, it's a snap and should be obvious how to remove the entire assembly.
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Cam a.k.a. CVOLVO.COM