Well after paying $4/lb to fill up on monday, I made some phone calls both to NX and then to some local welding supply companies. Found a place that will sell nitrous plus (form of nitrous oxide that you use for cars) to individual people. Other places had it, but you had to have a business account set up with them, which is why only places like Millenium, Performance Unlimited, etc usually has it.

Smallest quantity you can buy is 50lbs, at $130 a cylinder ($2.60/lb) and then you have to pay so much a year to use the cylinder that it comes in ($70/yr). So the first time you go to get a 50lb bottle it will cost you $200 ($4/lb), and you don't start saving money until you go through the first 50 lbs. Just thought I'd give people a heads up. Might be a good idea if you have some friends that use nitrous and you wanted to split the cost between 2 or 3 people. PM me for the business number if anyone's interested.