Well everyone, I figured out why you can't find that particular needle valve here in California... it's because it's got lead in it, and California doesn't like lead in their consumer products.
I went to the local Home Depot, and found a "lead free" version of the same needle valve, for just a few dollars more.
So, if all goes as planned, I'll have my ultra low cost rig up and running shortly!
I've got a new ASA on/off, gauge, tank, and needle valve for under $30. All new too. Muhahaha.
So, thanks for all of the info in this thread!