Really any 12 volt temp relay switch will work. As for the light bulb, you are correct. If the temp switch shuts off your pump at or just below freezing you won't need one.
Camp Wokanda
Peoria Park District
2023 - 210 on 3/16 shurflo, sap storage shack w/ 1100 gallon tank - 123 gallons
2022 - 210 on 3/16 shurflo, homemade vac filter & water jacket canner - 104 gallons
2021 - 215 on 3/16 shurflo, added 2nd membrane to RO - 78 gallons
2020 - 210 on 3/16 shurflo, upgraded hp pump on RO - 66 gallons
2019 - 150 on 3/16 shurflo, Deer Run 125 dolly RO - 73 gallons
2018 - 120 on 3/16 shurflo, 2x6 raised flue w/hood, homemade arch w/ AUF & AOF - 34.5 gallons