Wasn't sure what you meant by expensive until I looked up the Ring Stinger... but much cheaper than that you have the Fairfield Circuitry Randy's Revenge, which is the most musical and sonically pleasing ring modulator I've used, and then the Pladask Elektrisk Feber. The Feber has more features but is more metallic sounding and less warmly resonant than the Randy's Revenge. Both served me well when pursuing that ring mod sound.