Update:
Don't follow the direction of self-fixing the problem. It is not easy and not worthwhile. The correct part number is 45280-60510. The part can be ordered via the online shop at $115. Lexus will charge around $200 with bolts (roughly 20% above MSRP). The total cost of fixing should run you around $500 ($200 parts and $300 labor, $100/hr). Mention this site and the dealer would not likely overcharge you.
Lexus uses a cheap cast alunimum part that can't take repeated turns. For the new cars, you don't have to worry about that as the ignition is RFID-enabled touch button. No mechanical parts involved.
I hope this helps.
