Serious Eats - seriouseats.com

Where you source it from will depend on where you live in the country and whether it is rural or an urban center with diverse ethnic populations.

You can order it from many places on line. Also depends on the quality of the pork you want, how much you want to spend, and how much you care about the quality of life of the pig from which it comes.

I have read other people on the web having difficulties purchasing belly but here in NC it is readily available.

I buy it directly from farmers at the Farmer's Market but that means sometimes asking a couple weeks in advance, or getting to the market really early. Don't always get it skin-on this way though, just depends on the farmer and how they had it butchered. Most quality belly from these farmers goes to restaurants though.

If not there, then at an Asian market with a butcher counter. Always skin on, always a little more than I need, but I like making a lot of bacon at once, giving some away, and it freezes well.

good luck. great project.

Although where you find the belly will depend on your area, I wanted to point out that over on The Paupered Chef, the guys have dabbled in bacon making. They have photos, commentary, etc.