Spektr's rhymes with:
inspector's, inspectors, inspectors', specter's, inspector's, inspectors, inspectors', specter'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, specter's, vectors
Spektr's sounds like:
spectators, specter's, spectra's, subsidiaries, subsidiaries', subsidiary's