HELP please. Hot Water Heater needs new Thermocouple….

hello,
I have a 3 year old model #153331840 Sears Kenmore Gas water heater, and the hot water isnt working, it seems to be the thermocouple. I need Part #: 9007872 but Sears will take a week to ship it to me, so someone suggested home depot. they dont cross reference model numbers with Sears. What am i looking for at Home depot to be able to get a universal one. Iis it the length or anything else that I must compare and make sure my new one has…I did not take the old part out….and dont…

HELP please. Hot Water Heater needs new Thermocouple….