I copied this info from JCsS1MS at the Sims 3 forum.
{Link no longer good--02/27/14.}
Go To Main Menu & Enter In Thetestingcheatsenabled true
cheat.
Select the sims family that you want to find the keystone & wait for it to load.
Go Into Buy Mode & enter Inbuydebug on
and a question mark category will come up.
Shift/Click the ground & select BUY MODE.
Organize by category and select the question mark then choose the Crescent Keystone.
CTRL/Shift/Click onto the Keystone and select the keystone you need it to be.
Have your Sim pick up the key and then travel to the country to use the keystone.
You can also do this from your holiday location if you have a home there.
