Hey Adey, I'm about to pick up an 03 gx with nav and was trying to find the adapter you picked up. The link and website seems to be not available anymore but I found the yatour products on amazon. Was wondering if your adapter looked anything like this one...
YATOUR Car Digital Music Changer USB SD MP3 12pin for TOYOTA and LEXUS series https://www.amazon.com/dp/B007V9W8H6/ref=cm_sw_r_cp_api_4oKyxb6AMSREP
The table lists the 03 gx but it doesn't specify nav so I wanted to double check. I tried a tape adapter first and it sounded awful so I'm hoping there is still an alternative to get my phone hooked up! Thanks for anyone that has a more recent way for fixing this...