The Oregon 450 is the new version of the 400, perhaps with an upgraded compass and you can find it online (Amazon) for $325. You still have to buy the marine chart chip. I bought a 450 6 months ago and paid about $110 for the US chart chip. If you want street maps or topo maps, You'll have to buy more chips.
It's not cheap, but it works very well and has a noticeably higher resolution than the Garmin handhelds you can find at West Marine (for a lot less!)