Thanks to my geocaching friends,
The Neverlanders, for letting me borrow their concept
(GCM530).
This is a Where's George exchange. 
Add a new one to the cache, and spend the one you take,
after logging it on www.WheresGeorge.com.
It's free to set up an account
there, and fun to watch where your money goes.
You're looking for a small
plastic container, which on weekends, will be surrounded by
crowds of muggles. But with a little stealth, you'll manage
even with crowds.