For a polymer such as nylon , nothing much witll tend to start to dissolve it to provide a key. Acetone will work with polyesters. I can suggest something but personally I would not use it. Graffiti remover sometimes contains glycol ethers, which can attack your balls and make you sterile. Even the vapours from the remover wiill unlock the bonds in a plastic tail light. If you use it, breathe through an airline and don't get it on yourself. Applied to where you want to glue, it might provide a way of getting a bond. Don't use it near any other plastic parts - they fall to bits.
Looking at your photo, you might be able to glue-in a flanged plug.