The cold starting has been an issue for a lot of Captains from the very beginning. Trying to start a car engine with a lawnmower battery in cold weather doesn't always work. Some Captains have no problems whatsoever and others such as myself have had to wrestle with the issue every year.
I first tried the Odyssey PC-625 but it proved to be a false hope. However, prior to this last winter I install a Scorpion Battery and it made it through the winter just fine. This is a drop-in replacement for the stocker:
Scorpion Battery Replacement Battery For Harley Davidson # 65989-97B 12 Volt AGM Sealed Battery- Free Shipping
I don't know about a source in Auzland but if you can find it, it works well.
Also, a battery tender is a must in the winter.