Tom I don't have the scope or reducer ...but I suspect the larger scope needs a different reducer/flattener.
The part number from skywatcher is S20202. A search reveals ~$249 USD is about the price from many places like:
B&H
Highpoint
Skywatcher USA.
Amazon
OPT
The find USA
Anyway they all look similar pricing. Shipping costs can vary and some may not ship to Australia due to commercial area restrictions on sales by big companies...but some will sell and if not you can use a ship fwd company like
priceusa. There are lots of them.
Just do your sums on exchange/shipping to see if you really do come out in front, and enjoy.
Brendan