A Travel bug is a type of hitch hiker.
Travel bugs are tracked on Geocaching.com through a unique travel bug number imprinted on the tag.
Although it is possible to put travel bugs in caches listed on Geocaching Australia, we would rather you didn't because Geocaching.com does not track a Travel Bug through caches it hasn't listed. The Travel Bug would 'disappear' as far as Geocaching.com is concerned, eventually reappearing when it is logged into one of their caches again.
Travel Bugs can be purchased in Australia from Sphere Technologies. They retail for about AU$8 each.