Try Ebay. I have been successful here recently.
Buy the CD from Lexus and insert it into your CD player
To install the navigation CD in a Lexus GS430, first, ensure the vehicle is in "Park" and the ignition is on. Open the navigation system's CD/DVD slot, usually located in the dashboard. Insert the navigation CD with the label facing up until it is pulled in automatically. Wait for the system to recognize the disc, and follow any prompts on the screen to complete the installation.
Acuranavi.com
The Mercedes GPS navigation does require an installation cd. From what I read its a waste of money because they usually don't work. It looks like its cheaper to buy your own GPS.
I was looking for the same part ... and I got mines from EBAY MOTORS (ebaymotors.com) ... just type in "CD Cartridge for a 1995 Lexus ES300" and it'll pop up ... paid only $20
i have a 1992 lexus ls 400...the cd won't play..you can hear the cd changer ...but no sound
no.the CD is crucial for it to work
The 2009 Lexus IS-F has a drag coefficient of .30 Cd.
The 2006 Lexus IS-250 has a drag coefficient of 0.28 Cd.
The 2013 Lexus IS-250 has a drag coefficient of 0.28 Cd.
The 2007 Lexus IS-350 has a drag coefficient of 0.28 Cd.
The 2013 Lexus IS-F has a drag coefficient of 0.30 Cd.