I never saw sets in the catalogs. There was/is a distributor wrench that fit some distributors, not all, consisting of two L-shaped pieces with the box wrench on the short leg of the "L," and a male 3/8" end (like a ratchet set) on the end of the long leg. A double square female coupling linked the two pieces together, so you could make it a "U" shape, a sort of Egyptian "S" shape, or even with one "L" at right angles (looked at from above) to the other.
I own one, but I've managed to avoid using it for a long time now.