You will need a dewar flask for transporting the liquid nitrogen. Next, you will need to determine whether you are going to immerse the blades in the liquid or let them cool above the liquid. For immersion, you can use the dewar so you need to size it deep enough and have a wide enough mouth to handle the blades. For cooling in the gas stream you can nest a couple of coolers to let your blades set above the pool of liquid nitrogen.