Agreed, you should be able to run about anything "hydraulic oil" in nature, the power steering system is not very complex at all.
I had a buddy with an old Caddy that had a "bad" power steering leak and they were buying those tiny bottles of PS fluid.... yech!
I've started buying my oil in 4 gallon cases, Lucas hydraulic stop leak (same thing as the PS and trans stop leak that they sell at Autozone just in bigger jugs). My truck leaks a little where ever there is a connection. And there's a lot of connections!!