The 2005 Babies Galore catalogue has a Childcare Twin 'Rover' in it for $230. Weighs 12kg.
I remember when we were in Perth - Babyland had them, I'm sure lots of other stores do too.
Babies Galore have a website and online shop but no stores in WA.
The Rover has most of the features you want - except the shopping basket (well didn't look like it in the pictures, and didn't mention it in the description).
The Maclaren is $590 but the storage is not great for a big shop. It weighs13kg and comes with boot and rain covers and has other extras too.
Valco Twin Sports looks similar to the Rover but maybe not as compact as 'umbrella fold' - cost $300 and weighs 10kg. Again I don't think there is basket space.
Peg have a side by side twin stroller that weighs only 8kg and has a large basket (so it says), but I don't think it folds as compactly. Plus it costs $700.
A twin stroller can be such a hassle when it limits you to the wide aisles. Or just painful during busy times.
When my guys were little I had one in a sling and the other in the trolley.
Now one sits in the seat of the trolley and the other sits in the shopping section.
I use a great callio bag invention that clips onto the side of the trolley and hides the shopping so my darlings avoid throwing stuff out, or biting into fruit and veg.
(Doesn't mean they don't do it, but it's more out of sight, and they are still easy to distract).
I try to avoid the super wide trolleys as my two annoy each other (pull hair, bite etc) as well as having only one aisle to go through - not to mention wait at.
The other thing with the twin pram/stroller, is that you need an extra wide 'arm space' allowance when in shops.
You obviously know how one child can reach out for things as you shop, well a twin pram, which is wide enough anyway, can be a little more tricky, when you have one on each side.
Ahhh the joys.
Hope you find what you're looking for - I promise I won't post any more info - I feel I am now being a pain.
Sorry for the epic.