Hi there - I got your email but for some reason couldn't log in to OSW to reply ;p I don't hang out there much anyway.
Anyway - there are a number of places.
In Brisbane itself - Mr Toys on the Queen Street Mall has quite a bit of stock (including PF stuff) but the prices on general aren't great.
The Military Workshop on the north side of town covers some stuff but doesn't really have much in stock (claim they can order it all in though).
I've got stuff from Empire Toys in Perth.
Going slightly more afield there are a few online stores
www.figuremania.com.au (main distributer in Australia)
www.casefresh.com.au (excellent site - got many discounted buffy figures from them)
www.collectoybles.com.au
I also found another on-line store that is based in Brisbane - I plan to get Jabba off them
www.redrobot.com.au
There is also another store that used to be at Moorooka but moved to the Gold Coast last year - haven't seen that.
If you can't find it at any of them - then ebay is the best. Most brick&mortar stores place stuff on ebay - so using
www.ebay.com.au and search for Sideshow will generally turn up a list of retailers who may have more stock than what they are listing on ebay. Ebay also turns up the best prices in general - alot of the stores have some OLD stock sitting round so you can get lucky and turn up long out of stock product (I got my Black Knight that way - paid normal retail for it too!)
Until Jabba came out I hadn't ever had a problem. I still get most of my stuff direct from Sideshow though as the Australian Retailers tend to have quite a mark-up on the product - even after shipping its only about $A20 more for the Star Wars 12" figures so I try get the exclusive direct.
Figuremania has a long list of other stores that are "partners" and I'm in the process of visiting them to see what they have. Mr Toys at Springwood only has Dragon Military - I did pick up the two armoured Timeline figures from them for $A30 each though
www.oziegoods.com ocassionally has some good deals on product - but despite being local my orders have shipped direct from HK so I didn't really save anything on the shipping side - so if you find it cheaper elsewhere don't let the shipping charge from the other supplier worry you - shipping internationally is basically the same from anywhere to Australia.
Hope that all helps - if you have more questions feel free to post here or PM direct.