http://www.ebay.com.au/itm/Altronics-P0366-Adaptor-3-5mm-Stereo-Jack-Plug-to-2x-3-5mm-Stereo-Female-...
This is the only Australian seller I could find (in Sydney), and although not switchable, it should do the task you require.
Also, if you have a Jaycar store nearby, they should carry them as well.
