WARNING: Viewers are advised the following clip contains footage of a grown man licking his fingers a lot.
Note that I mention s'mores, but mostly in the context of chocolate-y snacks that have melty bits, not that they're somehow identical or anything (eat one after the other and they're pretty different).
UPDATE: Snacktaku EIC Michael Fahey has kindly pointed out that, for Americans, Tim Tams are available on Amazon. They're around *gasp* $10 a pack.
UPDATE 2: I'm being told that Cost Plus World Market sells them for like half the price Amazon does. So if you've got a store near you, that sounds like your best bet.