Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
stĭpŭlātor, ōris, m. [stipulor], jurid. t. t., one who demands a formal promise or covenant (opp. promissor, the one who gives the promise); a bargainer,stipulator,Dig. 2, 10, 3;45, 1, 41 sq.; 45, 38, 5; Suet. Vit. 14;Isid. Orig. 10, 5.