Specter's rhymes with:
inspector's, inspectors, inspectors', spektr's, inspector's, inspectors, inspectors', spektr's, collector's, collectors, collectors', connectors, defectors, detectors, director's, directors, directors', electors, hector's, injectors, inspector's, inspectors, inspectors', lechters, objectors, projectors, protectors, reflectors, sector's, sectors, spektr's, vectors
Specter's sounds like:
spectators, spectra's, spektr's, subsidiaries, subsidiaries', subsidiary's