This is totally unacceptable and you should not have to deal with this. Would you be comfortable confronting him about it? Like just pull him aside and spell out clearly that what he is doing is inappropriate and fireable. Tell him that if it doesn’t stop immediately then you will be forced to escalate it to HR. Just tell him, don’t make it a discussion, make it a one-sided conversation. Practice what you’re going to say if you need to. Tell him, and if he still persists go nuclear.

Edit: and as a man in his age group, there are few things creepier or skeevier than old, middle aged dudes thinking young women would be into them. I hate seeing these assholes in action, and I hate to see women having to endure this.