Quoted from DumbAss:You can purchase 7402 chips from Great Plains Electronics. Visit https://www.greatplainselectronics.com/categories.asp?cat=111 and any of 7400, 74HCT00 or 74HC00. Do not use 74LS00. That last bit is advice I received from someone. I replaced my 7402 with a 74HCT02 and it works fine.
Good luck!
Isn't the 7402 a NOR ttl chip, and 7400 a NAND? They're not interchangeable are they?