Buy a Battle Vest?

Hey guys, I know this is a weird question, but here's the problem: I'm 16 and I listen to a lot of metal. My dad also only listened to metal when he was younger, so he had long hair, etc. I'm planning on getting a battle vest and then covering it with patches, etc. My problem now is: How do I best ask my parents to let me get a battle vest? My mom has nothing to do with music, and she thinks it's all superfluous and unnecessary.

I'd appreciate any advice or solutions. Thanks in advance!