Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
pĕr-opportūnus, a, um, adj., very seasonable, very convenient or opportune: diversorium, Cic. de Or. 2, 57, 234: victoria, Cic. Fam. 6, 6, 6; Liv. 10, 45, 2.
Adv.: pĕropportūnē, very seasonably, very opportunety: venire, Cic. N. D. 1, 6, 15: fortuna te obtulit, id. Verr. 2, 5, 15, § 39: hoc cecidit quod, etc., id. de Or. 2, 4, 15: bellum sumere, Liv. 1, 42.