Maybe Plan C.

Today I found some 1" high-temp, high-dielectric shrink tubing, and as a form inserted a 3/8" rod into a 5/8"OD 3/8"ID hose. I shrunk four layers of the heat-shrink onto the form, and razored it to the right length. Looks great. Under the heat gun it softens somewhat, but I don't think that will cause problems in the car.

I'll wait a day or two and if no one cries "Disaster!" I'll install a couple and see what happens.