The easiest way to make another key is to copy the original factory one.

If you know which dealership the vehicle was purchased from and can show
proof of ownership, they may be able to get the key code for you.

You can remove the inner door panel from the front right door and look at
the key code on the lock cylinder.

You must also either contact a locksmith to "reflash" the ecu so I can
recognize the new key (which must have a transponder), or order a new
engine ecu. Our local locksmith charges $350.00 to reflash the ecu,
which is much less expensive but **may** not be as reliable as ordering
a new ecu from Lexus ($1500.00 +).

You must also "reflash" the engine ecu so it will recognize the new
key, which MUST have a built in transponder; the locksmith in our area
(Northern CA) charges $350 to reflash the ecu. This *may* not be as
reliable as replacing the engine ecu, but it's MUCH less expensive as
the ecu is ~$1500 plus labor.