How about the 16u USA topps set. There are about that many in it. I'm sure all the kids sign and you can get them via their parents address. Odds are one of those kids will turn out to be pretty good. It's also a set you could do every year and eventually you're going to land megastar. Just think if you did it in the past you'd have harpers plus some other highly collectible guys.
MAKE YOUR OWN CARDS!
BUYING ALL TOMMY THORPE USA panini cards