That's the one, Smelmechiz. The piston doesn't fire straight up and down like the old flat heads did instead they travel at an angle. Just make sure you get the correct shaft size.
If you want to buy local, the Briggs shop in Midland do a very good price on the things, or check out some closer shops. Two reputable shops that are a bit closer to you are Keogh's Mowers 'N More in Willetton and Forrestfield Mower and Chainsaw in, surprisingly, Forrestfield. Stihl Shop Cockburn may have some too, but I'm not certain.
