Make friends with an IT support staff at a US government facility and beg & bribe them to make you an email.
Either that or get a job in one of their offices.
All of those emails are highly monitored, so your chance of just buying one online is unlikely without going super blackhat and buying a stolen/hacked password, which is going to cost you a lot not to mention the serious jail time you can get.
This isn't just hacking; it's hacking a government-backed with some of the most extensive extradition clauses.
Good luck OP!