Not sure about Wa, have you tried merriartist.com. They are in Oregon. I just bought some things recently. It took 2days on the shipping. They ship same day as long as the order is in by 2 pm west coast time. They have a pretty good selection of just about everything.
Premier Paints on Beach Rd in Malaga ( Mario - good bloke) for DNA and Color Horizons brands, he also sells the waterbase Trident paints. If you want House of Kolor you may need to go see S&S industries in Midvale (Midland) opposite the TransPerth depot. They keep very little in stock but you can prepay to order it from East. If your wanting Createx / AutoAir paint I just order it from Airbrush Megastore in Adelaide..Steve is super helpful and has the best prices for paint & Iwata airbrushes, his postage charges to Perth are very reasonable too. I hope this has helped you mate.