I've been intrigued by lardo since I read about it in Bill Buford's "Heat" a few years back. I too looked for it, but alas, failed. All the Italians I spoke to knew what it was (their father or uncle or grandfather used to make it), but no one knew where to buy it.
I tried it at Babbo New York (as Buford describes Batali's version) and it was meltingly delicious.
I then tried to make it.
I regularly make pretty good cured sausage/bacon/ham/capicolli, so I felt Lardo wouldn't be too much of a stretch. Technically it was fairly simple: cured pork fat. My version, though, was lifeless and nothing like the dreamy, melt on your tounge, goodness I fondly remember from New York...some say you must start with GREAT pork to get good lardo - maybe thats where I went wrong? I dunno.
Fairmont butcher does cured pork lard, but it isn't quite my idea of Lardo as I tried in NYC either.
Update: the new Cochons tout ronds at the Atwater Market continues to carry ventrèche (and in larger pieces than the JTM) but… I don't know if it's my accent or that they don't know the product but when I say "lardo" they show me salted belly (lardons) and look at me as if I have a rutabaga on my neck when I say no. The search continues, but the ventrèche in itself is rather tasty as is the culatello.