need a little guidance

So I've been lurking on these forums for a little bit gaining knowledge of these vehicles from others experiences.

I have a 2001 Mazda Tribute ES with the 7 speaker system. I just got a new LCD in dash unit as a christmas gift and was excited to install. After looking at the wiring diagrams in the how-to I realized I would have to convert the sub out to an RCA in order to get it to work with my new head unit. I have done some searches on the forums and couldn't find an answer to my problem.

I am looking to keep the factory speakers and sub (for now, my car has a system in it that is loud enough). But I'm unable to find a harness adapter so that I can just plug and play. I have seen a few for the escape. Are the harnesses in the escape and tribute the same? If not where would I be able to find an adapter for the 7 speaker system in the tribute.

Any help is appreciated.