I have a job where I go visit customers a couple times a year, or more if they're really good at breaking things.
I honestly haven't found a way around the occasional question, but for the vast majority of customers they either act like they don't notice or just don't care. Some don't even make the connection. I typically end up unintentionally outing myself by being way too familiar with a system to be some new person visiting.
I have not had any truly negative responses. Either they're all accepting, or they realize that they need me there worse than I need to be there so they bite their tongues. My managers haven't heard any complaints so it's probably the former.