Have you honestly told him how you feel about this? Perhaps you could confess how much you think about it, and what (extremely sexy) things you think about in a "little" voice. It might rev his engine a little bit, just hearing how much it turns you on, and the fact that you're asking/begging/seducing him with it. I know that my Master has been open to things that he perhaps wouldn't have fantasized about on his own because I was a bit of a seductress in my manner of introducing it. Good timing is also important If it's not a "hard limit" then I don't see the harm in pushing for it in a sexy and pleasing way.

I don't actually know what to do about it if you have something that you consider to be an important part of your sexuality and it is not compatible with your Master, so I'm sorry about that part of the equation, but hopefully that's not the actual issue. I've had to bring up some pretty edgy, heavy, and embarrassing things along the way with my Master and I think the most important thing for me to overcome in getting the sexiness that I desired is getting up the courage to really openly communicate and ask for those things. After a while of doing that you become truly unafraid to bring up, share, and grow in your sexuality with this man and that brings up a whole 'nother level of intimacy.