Revvy you mean 6 months and bottle without stirring or disturbing and there is still enough yeast floating around to carbonate yeah? Who'd have thought!
Go to craftbrewer.com.au. It's in qld. I just got some sent to me in Victoria. $45 delivered and I worked out at 1.5ml per liter it should last me it should last me 20 years! Ha. Way better than the meta bisulphate. The smell and fumes will cause heaps of issues in confined spaces. Plus this...
Don't sweat it. People brew with only glad wrap on top and all goes well. Having brewed for years with 'normal' airlock fermenters the idea feels weird at first, but the science behind it is sound. I have done brews that didn't bubble because there was a seal problem, and they all turn out fine...