You can buy a 1 foot by 3 foot piece from this guy for $5.85.

http://www.ebay.com/itm/3M-467MP-467-MP-Double-Sided-Adhesive-Transfer-Tape-12-/120788742090?pt=LH_DefaultDomain_0&hash=item1c1f91efca

I found that a large rectangular piece is more practical than a roll for decals, as you can just pre-cut a piece of the sheet to size and then simply place all the decals next to each other on the cut sheet with no gaps or wastage.  

Shipping to Aus is $7.50US.

Hope this helps.