I don't actually know of any- especially not around my area (Perth Hills), but you could try going to a bakery and asking if they can make vegan cakes? Or perhaps ask them to tailor make a cake to your specifications?
Hahah. Hills Fresh IS a pretty good place for fresh produce. :/ Mados is tragically unreliable for fresh fruit and veggies, so HF rocks. Plus they have pre-made vegetarian meals like Dal and such. Although I prefer to make my own.
http://sweetassugar.com.au/ These guys are able to do vegan on request. And I know that Mimsbrook Organics in Vic Park can do catering, so I assume cakes also...
Hi, I have started a Vegan Dessert Business in Fremantle WA called Gaia Sweets!
Happy to make custom cheesecakes for birthdays and functions. Also available is Tiramisu, Mousse, Creme Caramel and more! Everything is vegan, gluten free and refined sugar free.