Go to a participating park and get it at the gate, so to speak. I hope they have not canceled the get it at a park system, very convenient.
Funny story; I got mine a few years ago at the Ocala National Forest Umatilla ranger station, I was initially refused as I did not present a valid ID, it was only a US Passport. Funny in a not so funny way, the girl at the counter, in all honesty, did not think that was a valid ID, she insisted on State driver license or other listed picture ID, not including a Military ID. Seems the list of vaild ID's did not include US Passports and, as usual, did NOT accept a military ID as one can have one and NOT be a citizen.