Maybe try ebay? Something like this?
http://cgi.ebay.com/ebaymotors/1997...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
or
http://cgi.ebay.com/ebaymotors/FORD...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
or even taller coil springs?
http://cgi.ebay.com/ebaymotors/97-0...ptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
There is plenty of stuff on ebay. Everything seems to indicate that the F150 and Expedition stuff is interchangeable, too.
That first one seems perfect! Perfect price and lift amount too. Thanks!