Hipshot makes replacements for MusicMan style tuners, which if they're the same as their American versions, should fit without any modification to the bass (screw holes align and the size is the same). I don't know what the weight difference is.
Hipshot HB1
If you really want weight savings, their Ultralight series are smaller and lighter, but you'd have to drill new screw holes and the ones from the existing tuners would be showing or you'd have to plug them up.
If I am not mistaken, MusicMan uses Schaller BM series tuners on their American Stringrays and Sterlings (Sterling model basses, not the Sterling by MusicMan instruments) which are good high quality tuners. Again, I don't know the weight.
Schaller BM
