Designers' rhymes with:
designer's, designers, designer's, designers, designer's, designers, decliners, designer's, designers, dinars, diners, liner's, liners, liners', meiners, miner's, miners, miners', minors, niners, niners', refiner's, refiners, refiners', reiner's, reiners, shriners, signers, steiner's, whiners
Designers' sounds like:
degeneracy, degeneres, designer's, designers, desmarais, desnoyers, deutschemark, deutschemark's, deutschemarks