I have had surprisingly good luck with Vets in Hamilton.
I went to Animates had a chat with the vet nurse told her I needed some Prazi, Vet was busy but rang me back same day, we discussed the medication as well as other wormers. she offer to get a some prazi in for me, just have to fill in a form to say why I want it and if I kill my fish she isnt liable..sweet! too easy.
Am trying to track down a small amount (less than 4 L) of Levamisole atm I will post details of the outcome soon