You can buy just the Aux input itself if you want. They can be found in any proper audio store. My neighbour put one in his boat, and I think he only payed like 10 bucks for it.
Or you can find newer ranger head unit, like 08+ I think, and they have them I believe. If they aren't in the headunit, I think that they have them in the vehicle, I think they might be where the air bag switch is