Liquid nitrogen is transported and stored in a vacuum insulated container, most common is a semen tank for storing cattle semen for artificial insemination. There is no pressure involved, the high pressure nitrogen cylinders are gas only, there may be large stainless vacuum containers for liquid nitrogen like liquid oxygen, I've never seen one that's mobile. If you're not looking to store liquid nitrogen, just one time use, then you could get a cracked semen tank cheap and take it directly from the supplier to your site. The tank won't be worth the risk to a farmer who may have his life's work invested in the genetics in a couple tanks full of semen and embryos.
Another option is dry ice/CO2, you can turn a CO2 tank on it's side and shoot out liquid that immediately turns to snow, put that in a container with your pin and some kerosene or gasoline or liquid propane to improve heat exchange, or wait longer for the pin to cool with just the dry snow. Or buy the dry ice, it's not hard to handle, good winter gloves are plenty, bare hands only if they're dry and tough. Don't move it in a car without all the windows down and moving.