First, check out Lard Lovers online.

Prarie Pride Farm sells ready-to-use Open Kettle Leaf Lard through the LocalHarvest website.

Slankers sells pork fat but appears to be out of it at the moment.

"Thundering Hooves" also sells pastured pork fat (see bottom of linked page) as either leaf lard or fatback.

To find more, try looking through the Eat Wild website.

If you want to know more about the specific fatty acids of lard read this blog post by Mary Dan Eades, MD.

You can use the directions below to render lard from leaf lard or fatback. (Source) This is apparently not the only method you can use. I've read references to methods that use an oven or crock pot but haven't found the actual directions. If someone else knows these other methods, it would be great to have them added here.

How to Render Lard

What you need:

• A pound or so of pig fat, either leaf lard or fat back. Leaf lard is the best grade of lard and is preferred for pastry, while fat back is the next-best grade of lard and is appropriate for frying. Each pound of fat will yield about a pint of lard.
• A big pot
• A lard stick (though a wooden spoon will suffice)
• Some water
• Some containers—Mason jars work nicely.

What to do:

1. Open your kitchen window.

2. After buying your fat, preferably from a farmer or butcher that treats its hogs humanely, chop it up into little pieces.

3. In a Dutch oven or heavy, large pot, add about a half of a cup of water to the pot, and then add the cubed fat.

4. On the stove, heat the pot on medium low, stirring occasionally (every 10 minutes).

5. After the fat starts melting (about an hour), you’ll hear some very loud pops. Do not be alarmed—that is just the last gasp of air and moisture leaving what will soon become cracklings (little fried pieces of pork). Now is the time to start stirring more often.

6. Soon after, the cracklings will start floating on the surface. Keep stirring frequently, but be careful—you don’t want the fat popping out of the pot and burning you.

7. When the cracklings sink to the bottom, the lard has been rendered.

8. Let it cool, and then pour it into containers through a colander or strainer lined with cheesecloth. The cracklings will be left behind in the cheesecloth and these make for a fine, fine snack, especially sprinkled over salad if that’s not too perverse for you.

9. The lard will be a yellowish liquid. This is what it’s supposed to look like.

10. Refrigerate it overnight and when it solidifies it will turn white. It will keep in the refrigerator for about three months, and the freezer for up to a year.