Replacement Pickup for Ibanez Blazer Bass

I have a 198(2?) Ibanez Blazer bass with a stock P-bass style pick-up (passive). I think I may need a replacement as the output from the D and G strings is much weaker than the E and A strings (I've played a little with the pick-up height without success). I'd like to replace the orginal pick-up with something similar as the stock pick-up has a real nice tone (brighter than my Fender P-bass). Does anyone know what would be a likely close replacement?

John