As in the film wetting solution?
I would try
Rewind at Broadway. I know they have some dev chemicals in store.
Not sure if they have many chemicals but you could also try
Sydney Super 8 in Newtown.
I've heard of people just using some heavily diluted washing up liquid instead but I haven't tried it.
P.S. I would have mentioned Blanco Negro, as they're the biggest, but it looks like they're closed until late September.