Most of the butyl tapes I have found are too wide and must be hand-rolled to reduce its size. The windshield setting tape I have on hand is 3/8 inch square.
This material is what's used for attaching the door moisture barriers. It's already in a 1/4 inch round roll and is narrower than the channel on the tail light housing. One roll should be able to do both tail lights.
https://www.amazon.com/dp/B...?tag=viglink20337-20 3M 08620 Window-Weld 1/4"
I ordered it through NAPA and it was priced at $12.20 for 1 roll, including Georgia sales tax. I went down to pick it up and they said that NAPA wouldn't let them sell one roll. I had to buy the whole case at $256.
I drove over to O'Rielly's and asked if they could get it. Their price was $25+ per roll but they did sell it by the roll. Showed them my NAPA receipt and they price-matched NAPA.