You can get regulators somewhat cheap on Ebay but I couldn't say what the quality of them are. Probably not great, but they'd only have to work once. I bought 2 regulators (for helium tanks, not sure the difference between helium tanks and nitrogen tanks, if any). You can unscrew the nozzle that blows the balloons up to attach the tubing. I was going to CTB months ago this way but I decided on a different method.
I don't know about anywhere else, but in the US you can rent regulars too.