Hi There,
To run these fridges from an adaptor you would need to fit a cigarette plug, or Anderson Plug.
If you do that, you can use the following adaptors:
https://www.mygenerator.com.au/evakool-heavy-duty-240-volt-to-12-volt-dc-power-adaptor-15-amp.html
https://www.mygenerator.com.au/evakool-240v-to-12v-adaptor.html