Can i use a Nikon SU 800 with other flashes?

I'm looking to find a cheap flash that will be compatible for my SU 800. I'm shooting with a sb 600 and SU 800 as my transmitter.

Are there any flashes that i can use that are cheap that will be compatible with my SU 800? I saw a Sigma EF-530 DG ST on craigslist. Could that be compatible?

The only 3rd party flash units I know of that will work (and even then, perhaps not 100%) are Metz flash units that have wireless capability. With flash units, you are far better off in staying Nikon (SB700, SB910, etc).