This may not be what you are looking for, but I have read here that MagnaFlow makes a replacement Cat for 3rd Gens for $300. It passes CA Smog, so should be fine for Federal rigs.
Hmmmm actually, there is a dizzying array:
2000 Toyota 4Runner Catalytic Converters | MagnaFlow
You might want to start the search over on the MF site - I did choose NY CARB/EPA but you may want to check my work.
Most muffler shops are MF resellers that could weld it up for $100 or less I'd guess. Support your local team