I know that Bunnings, and Masters stores in my state - Qld - do stock them but it is very seasonal. From expensive experience, I also found some lovely foliage ones were not happy with the care I gave them. Think you need a bit of expertiese with soil and watering, but maybe they were just not suited to a wet humid summer.
Anyway I was going to suggest you check out the society over there and may find sales days or links to members who might provide cuttings.

Here is a link that might be useful: geraniums and pelargoniums isociety perth

GAPSWA is definitely the place to be. They have sale days :)

They had plants for sale at Garden Week, and should have another one at the garden society fair in South Perth in September.

Locally bunnings gets in a limited range, if you are up North then Lansdale plants seems to have some stellars as well as normal ones at the moment.

Dear elaidlaw, have you tried Whistlepipe, or Miaflora or Beaufort gardenworld, or GuildfordTown nursery? I go round these regularly, and they usually all have some. Might be an idea to phone them to check for particular varieties available. I am also wondering about the Cottage garden club that used to meet in the South Perth centre once a month, the members there bring great stuff from their own gardens so you get things you usually can't access. Cheers, and good luck.