Representatives' rhymes with:
preventatives, representative's, representatives, preventatives, representative's, representatives, preventatives, representative's, representatives, additives, alternatives, conservatives, conservatives', cooperatives, derivatives, executive's, executives, executives', expletives, fixatives, imperatives, initiatives, laxatives, narratives, negatives, neoconservatives, operatives, palliatives, performatives, positives, prerogatives, preservatives, preventatives, relative's, relatives, representative's, representatives, superlatives
Representatives' sounds like:
representative's, representatives