A 600 came up last week. Just keep your eyes peeled and act fast. Go to alerts, alert preferences at the bottom right and setup an alert with the right keywords (SL900, streamliner). You get an alert as soon as an ad is posted. Check the usual suspects for used gear.
I hope you find one! IMO the 600 watt version is also very good. I've got both. I can't really run either to full power yet, but I expect the 600 to have enough power for most uses.