Sorry. I have to disagree with this totally. The workplace is so tense vis-a-vis sexual harrassment issues, among co-workers and even moreso between staff and management, that men will be very careful about doing anything with a female co-worker that they wouldn't do with a male co-worker. They might even be more likely to buy a bud a beer than a female co-worker.

Trust me... I was in this very position for a decade. A boss who wants to stay a boss can very easily 'turn it off'. Same is true for co-workers. Good jobs are too easily lost and men are feeling vunerable to the slightest misunderstanding.
I'm not a pro poker player so I probably do send out some small tells, but I definably feel I 'turn it off' at work.

As far as advice I can offer a good quote that seems wise even if I am not always good at following it myself. "A morning of awkwardness is far better than a night of loneliness". Sometimes life is too short to beat around the bush and an honest and direct inquiry can save days and weeks of reading body language, subtext and tea leaves.

Bring up the subject, make your feelings clear and then give the guy some time to think. It could be just what he is waiting for, or perhaps an exciting suggestion that he had never consciously considered.