White Electrical Tape
This is the perfect tape for your project if your lights have white wiring. Hard to find in the big box stores (they carry green as a rule of thumb), add a roll or two of tape to your order to finish out your project with a professional finish.
Installers use white tape to wrap around male-female plug end connectors to secure the connection, wrap empty C7 or C9 sockets, wrap the end of trimmed 18 AWG siring or to occasionally finish a lighting installation project where they’d like to use a quick nail but can’t.
Be sure to check the durability of any surface you apply this tape to in an inconspicuous location as it has quite a pull when removed.