Carrefour Express on Santa Fe in Recoleta (near Riobamba) has 28 oz. cans of Van De Camps Baked Beans (with bacon and brown sugar). They are not in the canned goods section, but are near the back of the store, on display above the fresh pasta.
The Disco on Esmeralda (near Libertador) in Retiro occasionally has them as well. Most Discos also have a good selection of La Costena products, including seasonings, salsa, and jalapenos. The Discos usually have US made peanut butter, too.