i have only seen two sizes. the one i am using, and a smaller one about half the size. i am sure they come in other sizes, but you wont find one.
the problem will be finding one. AirGas, praxair, airliquide are companies that would have the tanks. more than likely they wont give you one, but it wouldnt hurt to ask. i would first ask if they have any that are out of service, or very old ones.
File:Liquid nitrogen tank.JPG - Wikipedia, the free encyclopedia
this is a newer one, as you can see the outside is stainless just like the inner cyl.
you might be able to find an old one where the outside is steel and the inside is stainless.
new they are a few thousand dollars.
also, if its taken out of service they are probably going to drill a hole in it or cut it in half before they give it to you. tell them what you want to do with it, most people in my industry are intrigued by this kind of stuff.
you can also try welding supply shops, soda distributors(they sell co2 in these now for bars) any place that sells medical gas.
the bigger the company the more they would have, but the less likely they would be to give you one.