I want to keep my boyfriend from going on vacation
Why don't you want him to go on vacation?
No, but I'm afraid he might meet a girl with a sexier body there
You should be confident in your relationship with your boyfriend and understand that he loves you. Trust him and let him have a good time on his trip.
But what if he gets another girl while he is traveling?
If your relationship is strong, he won't stray away from you. Trust him and let him enjoy his trip. I'm sure he won't cheat on you and if he knows you trust him his love with you will deepen.