S.H.
Here some links for it:
http://www.busybuds.com/northpole/santa-key.htm
http://www.thriftyfun.com/tf60031690.tip.html
http://www.parentinghumor.com/activityecenter/christmascr...
http://theideadoor.com/Holidays/Christmas%20Pages/santas%...
http://www.geocities.com/cpgro1/holc.html
http://provo.craigslist.org/art/907328575.html
Also, on Amazon.com they have ornaments for sale and with the "poem." It seems there are MANY different versions of this poem. Just do a "Google" search, and put in the search word "Santa key" or "Santa key poem."
Hope this helps!
Good luck, what a great idea!
~Susan