Best parts place is www.rtbb.com.au
All your stuff at Bunnings will mostly be metric which won't be any good for the US spec stuff on your game.
Yep, as pinnies4me stated - RTBB have lots of that stuff, however for the items that RTBB don't have, I have been Googling the part numbers. You'll find that they will come up at some of the other places that specialise in pin parts.
If you don't have a copy of a White Water Manual to get part numbers from - try here
http://www.ipdb.org/machine.cgi?gid=2768Andy