Someone on here once suggested a website called Magnetic oil drain plugs cars, trucks, motorcycle, industrial. But you need to know your bolt size and thread size, it's not set up by make and model of car...
2G Prius is equipped with a small magnet on the tip of the transaxle ATF drain plug - so all 2G owners use a magnetic drain plug and therefore there is no need to buy one...
At least Gen 1 and Gen 2 come stock with a magnetic drain plug. I can't confirm newer ones do, but why would they quit?
Classic has a small rectangular magnet which is located on the bottom of the steel transaxle drain pan. You will need to remove the drain pan and replace the gasket if you wish to access the magnet, which will look like a swollen black slug with all of the ferrous metal particles on it.