HMV: HMV is another retail chain that sells music and entertainment products, including posters. They tend to have a wider selection of Australian artists and bands.
Music Stores and Record Shops: Several independent music stores and record shops in Melbourne specialize in selling CDs, vinyl, and music memorabilia. Some shops might carry a limited selection of band posters, including the ones you mentioned.
FYE: FYE Australia has retail stores in Melbourne and offers a range of music and entertainment merchandise, including movie-sized posters.
It's always best to contact these stores beforehand to inquire about their specific stock and availability of posters.