I've just ordered an EMG 37HZ set from EMG for $178 (AUD). They're passive, apparently the right size. I'll report once installed.
The ones that came with my IB-5 were so low in volume, that I thought the Aguilar preamp I put in was defective. I complained to Bestbassgear about the poor volume, and they sent me a new preamp, which worked exactly the same. So now I have to put the first preamp in another bass ha ha, but not with those shite pups.