Update
Hi everyone. my research finally took me to a product from a company called Yatour.
http://www.yatourcarkits.com/older-lexus-usb-sd-aux-mp3-interface-adapter-yatour-p-153.html
They have several options: Usb, SD & Aux input or ipod input. You can also combine bluetooth with any options. Price is very reasonable so i am very excited about this. However, to keep both the adapter and CD changer, i need to know how if it the CD changer that is directly connected to the head unit radio (CD changer port) or the nav system as i have not opened up mine before. I will appreciate any pointer on this.