Phil;

I'd call around to locksmiths to find one you can take the car to, to have a "Key made by Impression" technique...old-time locksmiths (lots of experience) who have a wall of keys (including hopefully the correct one, try "Union" key blanks), is required, these are available and hopefully on that wall.

Second option is to remove Lock Cylinder (trunk is usually least difficult to access, and simplest), take this to locksmith for same work. Once KbI is made which operates Lock Cylinder satisfactorily, have them made a few copeis obviously...hopefully door locks haven't been changed, so this key(s) should work there also...

Link to 122 key info (I believe many are the same as 544 so this applies, but 544 experts can/will please advise with details) info: http://www.sw-em.com/service%20notes.htm#Key_Blanks_doors_trunk

Good Hunting!