Thanks. I'm ordering the $40 dorman from amazon today.
DORMAN 923-231 Third Brake Lamp Assembly
ETA: The Dorman product has two minor issues.
1) The need to trim plastic and/or metal tab as described in this thread.
2) The overall width longwise is just about 1/8" too short on both ends. This leaves a very small slit for water intrusion on both ends. The product is not 100% fitted for the opening.
Pros: Looks stock. Functional.