Thanks for the replies guys, I'll check Igo's and Wesco out. Can you transport a CO2 tank in your car, or are there safety regulations regarding transport?
Modernhamlet, I am thinking about getting the rest of the system from AquariumPlant.com as well. Which regulator did you get, and are you happy with it? I'm wondering if their "Top Gun" is really better than the Milwaukee regulator. I've seen the Milwaukee regulator for sale for much cheaper at some laboratory outlet sites.
I don't think there are any strange regulations for transporting CO2, but it IS Massachusetts, so you never know! I wouldn't worry about it.
Alas, I just received the Top Gun a couple of days ago, along with the Milwaukee pH controller. The tank should be in the house this weekend, and the rest of the equipment is accumulating slowly, so no way to tell yet. From what I've read, the standard JBL and Milwaukee regulators are both good, but each has a little thing or two that annoys people. The Top Gun model is $10 more and corrects these problems. CO2 is the one area I'm new to and frankly, I'm willing to pay a little more for ease of use and dependability. My DIY time is going elsewhere!
I think Aquatic Plant Central
may have some helpful reviews.