Would love to do that but SWMBO would have a fit One step at a time I reckon.
Unfortunately I love the Grolsch bottles but hate the beer ... the six pack I had a while ago now contain all manners of herbal concoctions (bottles hiijacked by you-know-who), and I swore I'd never buy the stuff again.
Find a bar/restaurant that sells Grolsch swing top bottles.
Talk to the barman/manger - expalin that you are a homebrewer and would like to use them for homebrewing.
Strike a deal that you will come in on a weekly basis to pick up said bottles - getting them to rinse them would be really good - with some free home brew in exchange.
Should work a treat.
Alternatively, place an add in the paper.
While in Perth the Grolsch Rep would take the empties back from the bars/restaurants for 50cents ea and then on sell them for a Dollar each.
So, getting in cantact with the Grolsch rep - offering a deal with them could be a good way too of getting an unlimited supply of them.