[Hell to pay]

I've bought it a few times at a gas supply shop. You need a steel thermos and gloves. It will stay for about a day in your freezer.

[July 4th]

Thanks for the tips. I just went to a few of the websites of the chem supply stores I used to buy stuff from, and it looks like the real dewars are still expensive. However, I noticed Nalgene now makes temporary storage containers, good for a few days. That's all ya need.