I was in Bunnings yesterday, got what I needed, but had time to look out for grow bags, for fellow Workshopper, Trying (I was sure I'd bought some from Bunnings ages ago).
When checking aisles, I always take note of things that I can adapt/use to make what I can't find, so
things that I found that had potential to make use of:
A tarp of appropriate size that could be cut to make as many grow bags as required.
Multiple wooden garden stakes that will hold up the tarp while filling squarish or rectangular beds with soil, or only 1 stake/bed if round beds are preferred.
Some Gang Nails, (normally used to fix shade cloth) which in our case, will be used to secure the tarp to the wooden stakes.
If you'd prefer your grow bag to be vented, then randomly stab it with a sharp knife, or a skewer, once it's been filled with soil.
Bubble wrap, if you'd like some insulation, line the inside or outside.
Non-Bunnings sundry, depending on how paranoid you are about weed infestation, lay cardboard on the ground before setting up the grow bag(s).
Anyways, that's my improvisation, but I asked a Bunnings staffer for assistance, & found that ready made Grow Bags aren't stocked anymore, it was suggested that I check out a Disposable Skip bag which measures 1.3Mx1.3Mx1M tall, is tough as nails, & going for $15. I'd post a link to it, but Bunnings' web site won't cooperate. : (
If at Bunnings & want to check it out, it's labelled as a “BAG DISPOSABLE 1.3X1.3X1.0M SKIP JUMBO”.