There is no feasible way to ship small amounts of liquid nitrogen. If you do not have a container made for holding liquid nitrogen, we have found that a vented 2-liter Stainless Steel Thermos works very well. It is imperative that the Thermos have a hole drilled in the lid to vent the gas from the boiling liquid nitrogen inside. If a hole is not drilled in the lid, the pressure inside the Thermos will build up to dangerous levels, and a serious explosion could result. If the vent hole is too small, it may become clogged with frost.
Liquid nitrogen is just about as dangerous as boiling water, and for all the same reasons.
Like boiling water, liquid nitrogen can be handled quite safely if common sense precautions are taken. Like boiling water, getting a few drops on your skin will not cause serious injury, but any prolonged contact can cause VERY serious injury. Like boiling water, liquid nitrogen is always boiling and must never be confined in a sealed container. Items immersed in liquid nitrogen, like items immersed in boiling water, must be allowed to return to room temperature before they are touched. Do not use a fiberglass Thermos for liquid nitrogen since the fiberglass is likely to crack under the sudden thermal stress.