I'm a saxophone instuctor, and though I don't have any leads on used saxophones, I will tell you not to be afraid of used instruments as long as they are a reputable brand.  It is generally accepted that the yamaha student models are about the best student horns around, so you guys are right to try to find another one of these.  If it is in minor disrepair, you can have it repaired to as good as new and have just as nice a horn as a brand new one.  Don't worry about how shiny the lacquer is, all of the pros play on horns that have all of the lacquer rubbed off.  Instead, try to go with a quality brand like Yamaha, Selmer, Yanagasawa, Conn, Keilworth, etc.  I'd do a google search on an instrument before you buy it to see what others have said about the quality of that instrument.  We've had students come in with instruments bought new from Sam's Club for a fraction of the cost of a reputable brand, which are so cheap they can't be repaired.  The flipside to this are the professional players that play on King's from the 1940s which sound as good as the day they came off the line.  Quality over asthetics.