Jay Wolt (
www.qualitycards.com) has a bunch on his site at very reasonable prices.
Jay is one of the truly good guys in the hobby, and has been dealing with some very serious health issues. I know he'd make you a good deal, and there is no better to deal with.
http://www.qualitycards.com/psanonsport.htm
agreed it's a great set, one of my favorites. The artwork is amazing and the stories behind each one of the explorers incredible. Your kids will appreciate this for many years to come.