hi slash ... check out bartolini's website ... just google for "bartolini pickups" and check out the bass pickup section. I think they have a pickup that may just fit your streamer rockbass ... =)
changing pickups might help. so far the only exact model i've seen that replaces the dimensions of the stock pickup is the bartolini X44CBJS/CBJD pickups. there might be other similar ones but that you have to do your own research.
there are only a few guitar shops in singapore really. so you should check with them. alternatively, you can ask G77 if they can recommend you a shop, since you bought the bass from them. wouldn't it be better to start off from that lead instead of asking around again from cold?
also, do compile your questions. i know you have many to ask, but it would be easier to answer them all at once instead of having it piecemeal.