finding donors is probably not easy. Finding aftermarket parts is probably much easier, although I doubt your dealer will want to install them. Maybe a local technician will though. Check BEFORE buying. (unless you can do the work yourself)
You say California. But there is a difference between CA emissions and if you live in CA. Many vehicles are CA emissions, but this is not necessarily the same as CA legal. CA has it's own set of stricter laws.
If you live in CA, try this site. Good for information and they probably sell your converter(s), provided your Tacoma's EFN # matches their catalog.
www.californialegalconverters.com/store