Why not make your own? You save money and get satisfaction (or possibly frustration) of making the instrument.
Check out this site.....
http://www.didjiman.com/didjeridu/didge-make.htm
Others available as well as YouTube.
For a basic didg, you can use PVC and beeswax. 1 1/2" - 2" diameter bamboo works pretty good. The bamboo should be sufficiently cured/dried (not green).....minimum 2-3 months.
It's the mouthpiece of beeswax that's the key.......in addition to learning the re-breathing technique (never did master that part!).
Back in 1996, as an instructor at a primitive skills camp in NC, I heard an aboriginal play one at night when we gathered around the campfire.....beautiful sound.
Carl