FR - welcome to this wonderful little community...
Go to
http://www.boattraderonline.com/adsearchprocess.html and do a search on only 1968-1990 18-21 feet and seacraft as a name (and then use sea craft). Don't select boat type as some CCs wing up under sail and don't select price or location. There is a ton of reasonable prices 20's down there. I doubt anyone would like to trade but it's also a good place to sell your 24...