Thanks to dealbot on OzBargain for finding this. Seems to be first in first serve.
As part of the promotion for 'Amazon virtual-con' and the Amazon show 'The Boys', you can create a tshirt or tote bag for free and get it sent to you.
Link to Amazon page describing deal. Look for The Boys Supes Swag
"Just because we had to do things a little differently this year, doesn't mean you have to miss out on your favorite part of comic-con — FREE SWAG! Choose your item and create your own custom design inspired by The Boys. We'll send you your item free of charge once the event ends. One item per customer, while supplies last".
Despite many OzBargainers having issues with access to the website, I managed to choose a tshirt, design it and enter my details.
A bit of patience is required. Hopefully a blue & white tshirt arrives at my front door in the near future.