Fake flowers that are in large stocks are hard to find in Cairns especially if you are looking in the cheap dollar shops. This is hard if you are sending heaps via freight in a short timeframe but can be done.
Crowtex The Island Store do stock bulk packs of $100 for 100 flowers and $200 for 200 flowers and work out to be a $1 a fake flower, which is less than most cheap dollar stores and they are of the same variety and size, just different colours.
If you are looking for a different selection, be prepared to shop around to grab what you can. Try the cheap shop in Raintrees Shopping Centre, Silly Solly's in Showground Shopping Centre, The Reject Shops, small asian/chinese outlets such as the one near The Reject Shop in Earlville Shopping Centre down near the food court.