Teenage boys engage in risky behaviour because standard condoms are too big for them and if you offer them teeny tiny condoms they'll be happy to slide them over their newly-potent cocks? Have they met any teenagers?
I don't know where you can get smaller-than-small condoms, but the brands do vary so have you tried as many as you can? Some websites offer selection packs, and you should be able to find measurements for various condoms too.