Sorry haven't seen any around.

Comics R Us (on Bourke St) stocks old TFs and Minotaur (on Elizabeth St) tends to stock new TFs (but pricey) as well as other anime/comic/geekery stuff

Target (Bourke St) and Big W (Swanston St) both have TF Prime toys in stock but not alot. Target might be a place you could get the TF:Prime Bumblebee/Starscream 2-pack but that's not really a subsitute. (I want to get that SDCC pack too but have been put off by eBay prices)