Back in the earliest days of N Scale, Roskopf produced horse-drawn wagons in N Scale, which were imported and rebranded by Boyd Models, as well as Preiser. Three of them appear on page 3 of Roskopf's 1967 catalog; evidently a fourth wagon was made, a water wagon, but I've not yet found the catalog number.
Where to Buy
Very likely impossible. You might have better luck finding an old Boyd item.