Oh, yeeouch! There's always the local welding shop. They can weld, add bracing metal or both. Or a new frame.
Paul had our frame taken to Machinists, Inc. where he used to work and they did a scan of some kind and welded and added where they said it needed it, then Paul scrubbed down the rust, primed and painted it there with white industrial metal paint
. They helped us a lot with Peanut. It took several weeks.
Maybe call some weldshops. Some of them can make new frames as well as repair old ones. Gonna cost you.
We got a crane operator from Mach. Inc. to lift Peanut off the frame.
Old Peanut coming off the frame.
Repaired Peanut showing white tongue (white so I don't fail to see it and trip).
BEST to you; this is a vital job. We also found 4 out of 6 bolts holding shell to frame were rusted through; the other two were half gone.