David,
I just did a search for the Garmin 498. Seems they must have sold out on those units. I believe they only get a certain # of each refurb units and it's while they last type thing. Right now there isn't any smaller Garmin combo (plotter/sonar) units. Just a 545 with out sonar.
Keep your eye out on the link below. There is 4 or 5 pages of stuff.
http://www.getfeetwet.com/cat_garminrefurb.aspx