I really want it to fit nicely inside the KS doona cover that I've already bought.

Have been doing some intensive googling and found exactly what I need at Planet Linen (FYI for anyone else looking).

Plus the sales lady at the shop where I was asking was such a know all I just dug my heels in!

Thanks everyone!
I found this on Deals direct Duck Feather and Down King Single Duvet - 50-50% - Duvets & Quilts - DealsDirect.com.au Australia