well, if it were me, i would email the abc
http://www.abc.net.au/sydney/stories/s1108977.htm
according to that page it's only available in autumn, so you'll have a
little wait!
plenty of time to suss out a decent greengrocer and ask them to get one
for you later in the year.
or how about the vic markets?

Claude wrote:

Thanks Jils. What I meant was I didn't find much on Google that told me
what a gramma is. Certainly found a few recipes but nothing that told me
exactly what type of pumpkin it is esp if it is a butternut or not. From
the replies I've received and talking to my family it now seems clear that
it is not a butternut but a particular variety of pumpkin that is sweet and
usually (or else my mum only bought the curved ones) horse-shoe shaped. My
mum's recipe was to boil the gramma in well-sweetened water with a dash of
lemon and then mash and put in the pie shell. Only problem I've got now is
where do I buy a gramma in Melbourne???