I have a Shibari Mini Halo ($20 on Amazon) that I love. It’s rechargeable. And I’d consider it medium sized, but that’s probably a pretty subjective opinion - it’s roughly 8” long.

I'm around your age and ordered the Shibari Mini Halo off of Amazon. It's a great vibe, fairly cheap, rechargable (no batteries), and packaging is discreet of course. If your parents don't go through your mail and you don't have a credit/debit card, this is definitely the best option. Just go to your local store and buy an Amazon gift card. (It's almost 30 dollars, so the shipping is free). Happy shopping and have fun. They're a godsend ;)