Last time I checked, Hobby Dream on George St (Capitol Square) has XS-13 (Unit One from Evangelion 2.0). I can't remember the exact price, but it should be less than $150. They're the only place in Sydney that I know for a fact have them in stock.
I generally get my Evas online, though - I've seen a few XS-09s (Unit Zero in blue) on eBay. There's also XS-03 (Unit One from Evangelion 1.0) and XS-04 (Unit Zero from Evangelion 1.0).
XS-01 (Unit One from the original series) has been reported as having easily broken hip joints, something which was corrected in later Evas, including a reissue of XS-01 (XS-01R). If you're not fussed about getting the Rebuild version as opposed to the original version, I recommend XS-03 - it has an awesome Eva-sized gatling gun!