Here's what rhymes with rainbowl.
pole bowl poll toll dole bole boll tole dolour whole role soul coal goal hole roll sole fol mole stole parole knoll shoal droll foal thole troll vole kohl maypole prole stroll enroll cajole unroll condole skoal control patrol scroll systole extol petiole bedroll oriole extoll beanpole rissole innersole glycerol casserole vacuole camisole cubbyhole arteriole buttonhole decontrol pigeonhole profiterole quadrupole