So just to follow up, I checked with the Airgas branch that is a few blocks from my house, about 15 miles from Seattle. They do sell LN2, it's delivered from the truck that comes twice a week which may or may not have it on hand that particular time. Their suggestion is to leave your Dewar and they will contact you when it is ready to be picked up. The rep I talked to said no license is required required, you just need an account with them and a proper Dewar flask designed for the purpose. They didn't ask what I wanted the LN2 for and didn't seem to care. Getting an account is as simple as contacting them and providing the contact information they request.