The proper term for the area of rot is called the 'wheel arch'.
I am not aware of anyone selling small repair panels for these areas. Your cheapest route might be to find a donor vehicle in the junkyard and cut out the section you need, and then cut the areas to be reused out of the junkyard section.
You will need to use a welder. Riveting in these panels will be tough be insure mechanical strength AND water-tight integrity.
1992 XJ 2" lift -- RIP
2000 XJ 3" lift -- Australian Ford Big Brakes up front, rock rails, ZJ rear discs (with WORKING parking brake), C4x4 rear bumper/tire carrier, Hella H4 headlights, IPF driving lights, OEM skid plates, OME springs/shocks, JKS LCA's, JKS Sway Bar links.