word on the street is the Koolance pot is fine for dry ice but not good at all for LN2. Chris tested one at Legit Reviews and he knows what he is doing, he said the Koolance pot was garbage for LN2.
http://www.legitreviews.com/article/987/1/
another good alternative is a k|ngp|n bullet pot - the name is escaping me right now - but he doesn't have them listed on his site. not sure if Vince is going to make them anymore, but you should be able to find one used for a good price. it is a great little price/performance pot for LN2 and dry ice.
as for LN2, my only advice is to shop around...a lot. as an example, at Air Liquide in my town, they charge almost $6/L for LN2, but at Praxair i get LN2 for $1/L. the variances of price can be pretty drastic, so it is worth the leg work finding a cheap source.