You can find wild in the far eastern part of Vic, especially around Mallacoota, Chandler's Creek etc. It's pretty easy to find once you know what you're looking for; it'll grow on some bushwalk within 10-20 mins of the carpark (I can usually find it within 10-20 mins on any east-coast bushwalk I've done).
The variety that grows in the southern part of Aus is my favourite one, sweet sarsaparilla (Smilax glyciphylla). Lawyer vine (Smilax australis) has thorns and a much weaker flavour profile but I've recently become fond of its new season shoots/tendrils for salad use (see here).
Note that Hardenbergia erroneously cited above by Mandy is *not* the same as real sarsaparilla (Smilax species); its is false sarsaparilla. Its leaves look similar but it is a legume (Fabaceae), so I question its edibility profile (most native Australian legumes are toxic).
If you still can't find it shoot me a private message and I can arrange having some seeds sent to you in the mail.