Hi. I just had the very same issue and the good news is its a very simple fix. The car requires a "regeneration" of the catalytic converter. Meaning its blocked and needs to run hot enough to clean itself out. Take your car onto a motorway, select 4th gear and drive at around 3000-3500 rpm for 15 mins. This should allow the car to carry out the regeneration itself automatically. If this doesn't clear the lights, take it to a Toyota garage and request that they do the regeneration, only this time they'll tell the engines computer, through a laptop, to carry out the cleaning while they drive it.
That's all mine needed. No parts to be replaced.