TigerDirect.com has the Panasonic KX-P7305 duplexing laser printer on sale for $199.99 plus shipping and (if applicable) tax. There's a $70 rebate, and you can get another 2% rebate by surfing to TigerDirect.com from FatCash.com.
This laser printer has both USB and parallel ports. (You can add a network or wireless adapter at relatively low additional cost, since those are plentiful.) It also has lots of memory and built-in Postscript and PCL support, so it'll work well with eComStation. (Try the HP LaserJet 4 Duplex driver if you can't find a better match. That should work fine for 600 dpi duplex printing with this printer.)
As always, check the cost of consumables ahead of time.
I have no affiliation with these companies.
Source: Timothy Sipples