If they have the original key with a reddish brown head and that key is OK, then I think you can buy a new ignition switch with keys and then swap the chip from the old red-brown key to the new similar key and go from there. The ECU and the old key are paired, not the ignition switch itself. Scooterpartsco.com will sell you the switch for $239
https://scooterpartsco.com/ricambi/030-piaggio/ignition-switch-and-keys-for-piaggio-mp3-624441?zenid=1c47fc09865d4f14532c133c9f4b91a0
If they don't have the red-brown key it's a bigger deal because you have to send the ECU to ScooterWest and they will "revirginize" it, for another $100 and some dollars.
Getting these parts off and back on is a major job. Paying for it all to be done for you could run close to $1,000 I would think.
I just did this on a 2008 MP3 500 I got from a tow away yard in San Francisco. It all worked and the scooter is ready to sell, but with this plague going on I'm waiting. If you want to know more, send me a personal message or reply here.