bass gtr efx pedal: looking 4 clean sustain, boost harmonics

What pedal can anyone recommend for a clean sustain and to boost notes where false harmonics are applied without blasting the overal normal notes.
My first thought would be to get a limiter. I have a compressor built into my amp but that is used mostly designed as a protection peak/limiter device circuit to even out string attack.
My first thought would be to get a limiter. I have a compressor built into my amp but that is used mostly designed as a protection peak/limiter device circuit to even out string attack.