I suggest:

a) producing a preview yourself
b) approaching a local company that does readings (either amateur or professional, although pro companies are extremely difficult to get a reading from)
c) submitting it to a competition for musicals (there's a site called Musicals Australia I believe that has info on stuff like that)

Off the top of my head, I can't think of a single place that you could just call up and work with - for all of the venues in Melbourne you would have to submit an application (I refer to their offers throughout the year for subsidised space and/or marketing support) or hire the venue and produce it yourself.... Your best bet is option a. And perhaps a government grant.

Seahorse shadow puppet for sale at
Puppets in Melbourne