Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
prō-mercālis, e, adj. [merx], that is dealt in, that is bought and sold (post-Aug.): res, Col. 1, 8, 13, 11, 1, 34: vestes, Suet. Gram. 23: aurum, id. Caes. 54; Gell 4, 1, 23.