Mate I know a million but I really doubt ull find any who will go through the effort of registering overseas players etc, just for you to play 1 game ( if you are available for 3 weeks over here, you are only available for one match as we play two day matches.
As well as that most strong clubs already have there max number of 3 overseas. You would however be welcome to train with any clubs around Pymble such as Northern Districts, Macquarie Uni, Gordon, Pennant Hills or Epping.
I guess the other thing you could do is go down to a club not tell them you are levaing in 3 weeks, just play 1 game for there 5ths and go.