How to convince my parents to let me get a chastity ring?

I'm turning 14 on the 6th and I really really want a purity ring... I understands what it means and everything but my dad is against it because it thinks that once guys see it, they're going to think of it as a "challenge" to see if they can get me to go that far which I highly doubt. How can I convince him that going into high school, I wanna make that vow and I'm gonna stick to it and that whatever he suggested isn't going to happen.