[drlevy88]

Based on what I googled up with "liquid nitrogen" "price" "liter" this recipe might use $9 worth of the stuff if bought in that small quantity at retail. Not counting the dewar flask (dunno if Thermos bottles would be good enough).

[ALS]

Actually a thermos does work, but you have to be veddy careful transporting and it won't last long, so use it quick!

Small chance they'll let you walk out with a thermos full though.

[Tijeras_Slim]

A themos bottle is a dewar and would work, you just don't want to close it tightly, as LN2 expands by a factor of almost 900 when it changes to gas. I get 230 liters for about $180.