Actually, at this point, if they're a reasonable price, I'm willing to drive to Philly to get them (it's about three hours from here). I'm in 16823 (Bellefonte, near State College).
And, yes, they're legal to own in Pennsylvania, but you cannot ship them over state lines, and if you obtain them by having them shipped from another state, they'll be confiscated. You MUST obtain them in Pennsylvania, and you cannot cross state borders with them. Plus the ethical side of it... you can't release them (shouldn't release ANY plant/animal, whether it's invasive or not) and you should keep your tank 100% escape-proof, as well as use caution when doing water changes if you have babies, plus you need to be responsible with any eggs or babies, to be sure that they don't make it into the wild or into somebody's possession who might not be as responsible.