I got these globes at a Wal-Mart years ago in the school section for $4 each. I used acrylic paint that I already had at home to paint them. For the land/water globe I painted the blue first. Then I painted white school glue (or was it Tacky Glue?) in sections so the glue wouldn't dry before I got the sand on it. The sand came from our sand box. Note: sift the sand first or your Australia may have a big 'rock' on it like mine does. [*Then* I sifted and the rest came out just right :)] Once you paint the glue on a section roll it in a bowl with sand.
I actually like this smaller size for our home school. They are about 4 inches in diameter. I got a third one and just left it plain with the details. Just last week youngest dd was using that one. I saw some almost this size at the local dollar store a few weeks ago - also in the school section.
If you need the full size or a commercial Montessori Globe I found this one on Amazon: