You will have to be careful who you approach of course because I guess you do not want your fetish made public.Do you have a female family member who you can trust and maybe ask them to buy some for you.I would be careful of asking an older male even if you could trust them.When you are a little older then you can of course buy them yourself under the pretence of a present for a girl--good luck dear.
Im a straight teen boy and i like wearing panties when I'm by myself but want some of my own because I have to wear moms. I know my parents would never let me. How do I secretly get some?
Buy a pair or 2 next time you go to the store! Just go look to see if you like anything pick them up and go pay for them, nobody looks or even says anything! I do it all the time!
Just go to a store and buy some, you are a teenager you should be able to go to a store on your own. If you live in a big enough town go to a random one where they sell panties grab some and buy them. Whatever who cares who knows? People are people, if the person you are buying them from actually asks - which I doubt they will - just say you are getting them for a girlfriend or your mom asked you to pick some up for her while you were out.