I want the paint to somewhat match the car with 80k miles
but new is an option, thanks!
If you check, like on ebay, there are outfits that specialize in oem paints in shake cans. Good stuff. Kind of pricey these days. But a can each of primer, base, and 2 stage clear coat should be about 50 dollars. Toyota has for decades used extremely high quailty paint I doubt you'll notice much fade (except maybe with red?).
Besides if there is significant fading it will be nearly impossible to find a fender that's faded in a similar manor. Let alone a straight one. In my experience used body parts are false economy. If your in a medium or large metro area there are automotive paint suppliers (yes some auto paint suppliers can put it in shake cans, call around) that might, for a price, mix a custom shade to match your fade. Maybe even consider having a shop paint your fender before you install it.