I got this in an email from Rivers:
"New Management Shock Clearance Sale begins Wednesday 8th Jan
As you are a loyal customer, we wanted to let you know that over 1.5 million items are being marked down to as low as $1, $3 and $5 on Wednesday 8th Jan. So hurry in-store as they won’t last long."
The current 50% off sale is pretty good, I imagine this will be even better. I can't find any further info on it yet but the above implies it's instore only.
Tried their seam free undies. For $4 they are pretty good.