Rivals' rhymes with:
rival's, rivals, arrivals, revivals, rival's, rivals, approvals, archrivals, arrivals, carnival's, carnivals, crovls, daredevils, devil's, devils, devils', evils, festival's, festivals, hovels, intervals, level's, levels, marvel's, marvels, nevels, nevils, novel's, novels, removals, revels, revivals, rival's, rivals, shovels, sivils, swivels, travels, unravels, upheavals, weevils
Rivals' sounds like:
rabalais, rafalski, raffles, ravel's, rebel's, rebellious, rebels, rebels', rebholz, refills, reflag, reflex, reflexes, repeals, repels, replace, replaces, replays, replica, replicas, replicase, replies, republic, republic's, republica, republics, republika, repulse, reveals, reveles, revels, revivals, rifles, ripples, rival's, rivals, robles, ruble's, rubles, ruffles