My favorite Christmas market is coming up on December 10-11. It's only about a 15 minute bus ride from Kaiserslautern. With handmade and local goods and delicacies on offer, and set on grounds that abut the woods, it's a charming market.
Check out my more extensive guide that I wrote last year, with this link.
To experience fewer headaches with transportation, take the bus from Kaiserslautern. Driving there and parking are a nightmare but the bus is worry-free.