These are the slides I used
762mm 227kg Locking Drawerslides Fridge Runners 4WD Cargo Trailers Free Postage | eBay they took about 14 days to be delivered to me in WA.
I like the idea of a full barrier, but as you said they take up space, and would mean access to the gas bottle & recovery gear hide aways would not be possible.
My cargo barrier will be a 1/4 barrier that will attach the the top of the unit, and somehow attach to the points behind the trim above the rear side windows. Or possibly using a strap to pick up the centre child seat anchor above the rear door. The barrier will more then likely be a modified one from the local recycle place, they always seem to have Falcon & Commodore ones
I'll do some photos of the door shelf later and post them.