The stickers can be purchased at:
Packs (5 stickers per pack) EB Games $3 and JB Hi-Fi $3.
Box (36 packs per box) Gameology $84.95 (avg. $2.36 per pack)
You should also be able to buy them at a newsagent?
There are also trading cards which can be brought at:
Packs (6 cards per pack) EB Games $7 and Big W $6.50.
Box (24 packs per box) Gameology $125.95 (avg. $5.25 per pack)
I don't think McDonalds purchased the rights to use the Australian uniforms
*Edit: the stickers look a lot different to the Panini WWC23 stickers. Panini Official Release McDonalds Release