Randomly came across a $5 Otterbox Defender case for a Galaxy S3 at Big W in Taigum (QLD). Brand new and sealed. Was the only Otterbox that I could see so I assume stock levels are low. Other stores may have cases for other model phones.
Scans as "MOBILE ACC SPECIAL" and part of a display that had quite a lot of other accessories, but nothing reduced as much the Otterbox. This should be nationwide as it comes up on the self scans and has no replacement barcode on the box.
Might be worth a shot if anyone sees them in their travels.