Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ostentātor, ōris, m. [ostento], a vain, self-satisfied exhibiter, a displayer, parader, boaster, vaunter: ostentatores meri, Plaut. Curc. 4, 1, 15: ostentatorem pecuniae gloriosum describere, Auct. Her. 4, 50, 63: factorum, Liv. 1, 10: omnium, quae diceret, Tac. H. 2, 80: rector juveni et ceteris periculorum praemiorumque ostentator, id. A. 1, 24.