Translation:Who are you looking for?
Whom dost thou seek for
should be correct as well, as I am speaking about the end "for" being acceptable at the end of a sentence (if his statement is indeed correct and needs a "for", contrary to what i see, unless "seek" in old English needs a "for"), contrary to what many think is wrong. It was normal to end sentences with a proposition on old English (considering this is old and not middle)
"Who are you looking for" definitely sounds more natural if you're asking what someone is doing at the current moment. "Who do you look for" sounds like you're asking the person who he looks for habitually, as if he works as a hiring manager trying to find suitable people for a job.