On eBay there is a seller of silk abaca. I am waiting for him to respond through Facebook. It's actually the guy from "hat blocks wagga' he has a Facebook page. He sells 5 metres on eBay for $175. Which for 50cm is about $17.50
If you mean for making flowers I use Silk Trader. They are in Victoria but have very reasonable shipping options and will send samples. They have a great range of silks in many colours and Kevin is super helpful. I make all of my flowers with their dupion. You can find them at www.silktrader.com.au