You're assuming these guys see this as a problem. I suspect for most of them, the power issues are, erotically, the whole point. Why patronize a prostitute for make believe alpha male abuse of one's position when one has the real thing every day?
Maybe if you could pay prostitutes for them as a third party in some way, that could work.
Because it's a lot less likely to get you in trouble (if we make it a lot less likely to get you in trouble).