I've used metal struts I make on a workbench and 2 part epoxy to fix such things. I've done this a few dozen times over the years but there is no set procedure. You look at it, then craft a solution. Here's some of the usual source material.

2 part epoxy
Painters tape (to keep glue and paint off other areas.)
Metal bits. Sheet metal, cut to size.
Small nuts and bolts if need be.

The real repair is to order parts, etc. but you want to create a fix that will hold for a year or so.