you can the Thai Business directory, visit the food shops http://www.wat.austhai.biz/Home/wa-thai-businesses

I do know if you visit the Thai Temple in Perth on the Sunday and ask you'll finnd many Thai's living in Perth have these trees at their homes and some will then give or sell you fresh produce

to visit the Thai temple try this info http://www.wat.austhai.biz/Home/BSWA