Its probably near the comic shop. There are three or four collectors shops all clustered together. There is the comic shop, the movie toys and memorabilia shop, a goth wargames type shop and a fantasy clothes shop which stocks "alice in wonderland" type fashion, big 1900's style dresses etc for alternative street wear. ( shops from memory )  I had a look and it is in a side alley in the Citi centre arcade off Rundle Mall . Great little place to stumble across.