I got an aluminum cylinder for $50 shipped from kegerator.com, but they're more expensive now. They look a lot nicer, IMO.
For what you'll pay to piece together a co2 regulator, you might as well spend the $89 and get a complete kit, with a solenoid, at eseasongear.com.
FWIW, I let my cylinder run empty twice and never had an issue... I don't think it's nearly as big of a risk when the cylinder is upright, vs on its side.