Geez. I always recommend never mixing business with sex, so if it were me, I’d walk. I like my career too much to risk it.
However, if you aren’t in love with your job and don’t mind changing jobs if this goes bad, maybe hint a little at things with word play, and see if he bites.
Make the setting easy for him so his roadblocks are minimal. For example, visit him in his office 15 minutes before closing on a slow day, like the day before July 4th three day weekend when the office is light, and then lay it on thick with the sexual innuendos.
If he is a ‘alpha’ type, or better yet, a guy who takes what he wants, he will take you. If he isn’t, you probably don’t want him anyways.
There is always the possibility that he will have the same philosophy as me though – never fuck a girl at work. My career is too important to me to risk it on some trim.