I couldn't find anything under a dollar off the top of my head but you can grab one of these to use up instead of buying something you don't even need.
Permatex 09980 Counterman's Choice Spark Plug Boot and Electrical Connector Dielectric Grease-4 gram pouch https://www.amazon.com/dp/B000HBNVH6/ref=cm_sw_r_cp_apa_pzi0xb8Y2J47X