The place I use and recommend is nippon-pharmacy.jp. This place looks pretty dodgy when you click it, but I have purchased 6 months worth of Finpecia and have had no problems (except for somewhat slow shipping since it came from India and not Japan).
The prices are dirt cheap which also seems dodgy at first. You can get 3 months supply of Finpecia for 50 bucks. Or if you cut up your pills you can get 100 Fincar tablets for 70 bucks, which would work out at over a years supply, so that is insanely cheap!
This place is 100% legit and the only reason I sound like I'm promoting it is because it's the store I use and I don't want it to close down. Plus a lot of the popular "trusted" stores people use here don't ship to Australia such as United.