First, welcome.
To answer your question, go to a locksmith. I had the same "no key for my trunk" problem years back for a newly acquired used car. A locksmith got the trunk open, lock cylinder out, new keys made and cylinder reinstalled in 30 minutes (he answered the phone a couple of times too).
Jim
Thanks for the welcome. We are having troubles here locally having a knowledgeable locksmith. But it has got me to learn a lot about locks.....
I made good progress this evening. I had already planned on opening it myself (if I could figure out how to) and handing the cylinder to the locksmith. Well, you can get into the trunk by pulling the rear seat! Then I decided to try the keys we found again. He had changed the ignition key switch so I figured out we have at least 3 keys to operate this car. (I say it this way because I can't get the passenger door lock to work. Yet)
I will tell you all: You NEED to get a can of Houdini 4-Way Lock Lubricant. It works better on locks than anything I've ever tried. It often runs $20 or more for a 11 Oz. aerosol, but it's very worth it! Keys and Locks work better than new!