The license-plate holding area on the back of my bus is completely rusted out (by completely I mean there's about a one foot by one foot hole where the license plate used to be mounted). I'm going to repair this by riveting a sheet over it, but I can't reproduce the original slightly recessed portion that holds the license plate.
Instead I want to cut an opening and mount something like this frenched steel license plate box: https://www.ebay.com/i/183117167652?ul_noapp=true
Problem is I'm not up to welding sheet metal like this (which I think is how these are generally attached) so I was wondering if anyone has ever seen a box like this that has flanges on the front, such that this box could be riveted into the hole instead of welding. I have a sheet metal brake so I could make my own flanges and rivet them to the box and to my replacement sheet, but I'd rather have one that came with the flanges already.
Also, has anyone seen one of these boxes with four rivnuts installed instead of just two? There is a frame that includes a light that I was planning to use to mount the license plate, but it would be more solid with four mounting holes instead of two.
Or I'm open to better ways entirely of handling this.