Kroger had pre-diced pancetta. I've used it before, and it renders more than enough fat; 2-3 TB from that little plastic tray. It's what I used for mine (both dishes), and I liked it.
As to what I'd do in your situation...I'd always go with best local ingredient. Think about it: part of what makes a dish "traditional" to begin with is that, way back in the old days, the cooks who were creating these dishes for the first time used the best that they had on hand, available locally. I doubt if the first person to make carbonara said, "Right. I'm making this dish, and I think instead of a red sauce, I want...eggs that cook just from the heat of the pasta. And little bits of meat in there...salami won't do...nor will prosciutto. I know! Guanciale! Nothing else will do!"
No, more likely, they said, "I'm hungry. I've got pasta, eggs, some cheese, and this hunk of pig cheek lying around. What can I do with that? Oh, what the hell, I'll cook the pasta, dump some egg and cheese on it, and chop this pork up a bit for some meat. There. Supper's sorted!"
Not to get too touchy-feely, but to me, using the best, though not exact, ingredient, pays homage to the spirit of the people who first developed it, to their creativity in using local ingredients.
