Factory RTV tyre size is 215/65/16.
But you can go bigger
[EDIT] I've found one RTV alloy for you on eBay;
https://www.ebay.com.au/itm/282436003458
It shows the offset markings you're looking for behind the spokes in one of the photos.
[EDIT again] These could work;
https://www.ebay.com.au/itm/201829753438
Aftermarket but quality CSA (from when they were made in Australia), even lower offset 10P (same as what I run), load rated to 900kg per wheel which meets the 1-tonne requirements. On special - make an offer.
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