Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
obsōnātor (ops-), ōris, m. [id..], a buyer of victuals; a caterer, purveyor: obsonator optimus, Plaut. Mil. 3, 1, 73; Mart. 14, 217 in lemm.; Sen. Ep. 47, 8.