I had these guys install one on my 98 LS400. I requested to have the jack installed on the back of the radio so I could run a line to ashtray. A switch was installed next to the radio's volume control for ease of use. Cost was about $115 and turnaround time was real fast. They can do just about any and all radios. See photo below.
http://factoryradioservice.com/lexus-aux-modified-radios-c-41_42.html?page=1&sort=20a