As far as I know there is no Australian Insurance company offering Covid 19 insurance. You can take out cover with a Thai insurer such as Sawadee AXA for the length of your Visa.
I am an Aussie and had the same problem today. I took a snipet and also took a pic with my phone but no luck after trying many times. At the end of the application your able to upload extra documents so I uploaded the QR code there.
I bought covid only insurance $170 aud for 90 days with cover $100,000 usd I already have travel insurance so no need to double up of course. AXA make you buy travel insurance as well as covid