Hmm. Power pullstart. The RB is a great choice, as is the NovaRossi or Top pull start versions. Choices are a little more limited, but if you want to keep a pullstart, you can't really go wrong with those. Check to make sure they come with a threaded crank, or you may have to do a little work with the clutch you have (at the very least you will need the sg clutch nut). Depending on the size of the pullstart mechanism, you may have to add a spacer or two between either the chasis and the motor mount or the mount and the engine. I had that problem when I had my pullstart OS. Can't really say what the price on any will be in AU (I'm in the US).
Going bump start does have it's advantages, though. You will have a more powerful engine, without question. And you won't have to worry about tugging that pull start cord to get it to fire up on the day the tune is just slightly off and it does not want to start. On the flipside, in addition to having to buy the starter box, most bump start motors are rear exhaust, meaning a new pipe as well.