What was the specific problem with ITA?

I can't say that I know of any LAX- or SNA-specific means of searching. Honestly, I'd probably just go through ITA and check with my preferred airlines if I were you.

Alternatively, you could check to see if there are any cheap flights into one of the Skyteam hubs and book a separate flight on WN (WN flights don't come up on ITA). That combination might be cheaper. But, it might not be worth the hassle.