Hi there & welcome
They do in fact come up on TM fairly regularly,
like this one
Not in Auckland but you get the idea. That one also happens to be Synta-made, like the Skywatcher and virtually identical to it. There isn't much between those and GSO's optically, or ergnomically though.
So, keep an eye on that site. Search for "telescope" rather than "dobsonian" & scroll past all the junk. Many dob sellers have no idea it's a dob they are selling.
Yes get an 8" if you can but don't lose any sleep if a 6 is all you can find in the time you have. Still a
very capable instrument.