Sewer line location help

Hi all - we have already gotten the drawings from the county and started digging with no luck. Our home has two sewer lines going out to the main line. We are hoping to add cleanouts to these and have found one, but are really struggling to locate the second. Hoping someone might have referrals to a locator-type service or other ideas? The last time we had our sewer line scoped the guy couldn't get his camera past a particular turn so that seems like a dead-end too. Hoping to not have to dig up and destroy the entire property in the journey to find this thing.