99 Suburban - add aux input?

[79Silv4x4]

I have a 99 Suburban that has the factory AMFM/TAPE head unit and the factory slave CD player. I just want to add a simple aux input to this setup to connect my iPhone to stream iheart radio, pandora, etc. Looking for a low cost solution and I don't need to be able to control or charge the phone, just need to get the tunes from the ipod to the factory unit. Any suggestions would be appreciated.