3M Australia seems to not want to know about this product and freight from the US as you have discovered is horrendous these days.

So in your case I would hotfoot it down to the nearest Blackwoods store as they stock two brands of butyl mastic tape to be found here.......

....... www.blackwoods.com.au/gasket-material-packing-seals/bandages-anti-corrosive-pipe-repair/butyl-mastic-petrocote-pcs/tape-butyl-mastic-50mm-x-10m/p/02716566

There is also a butyl mastic available in a cartridge, but boy, is it messy if you're not carefull. (don't ask how I know) available at Bunnings et al.

Of the two that Blackwoods sell, one, the Denso brand is listed as being potable water safe.

I had told you not to ask , but since you have ......

I used the soft gooey mastic many years ago in a caravan in which I was resetting the windows. It's an ideal product where you need to have lots of joint mobility combined with the likelihood that at some point in the future you may need to take it apart again. Sikaflex make one as do Selleys and Bostik.