There are a few ED units you might find close to that range, but the mount would be extra. Be aware though that most Plasma's in that price range will be industrial or commercial models and are probably not HDCP compliant. Which means that a DVI cable will only work from a computer and not a video source.
Look for these brands
Champion
Electrograph
LG (MU-42PM11 might come close to the price)
Wall-Mart has some "off brand" stuff below that price.
Gateway had one (don't know if they still do)
Maybe Dell