thanks for the replies everyone.
I saw that one adapter, but the incoming 13 pin (from the cameras) also has male pinouts. If I could find a 13pin din female on both sides, I may be able to work it. Believe it or not, Magnadyne has cables for each individual camera to RCA, which have individual 5 pin triggers for 12V.
But, after looking at this in depth, triggering each of the 3 cameras individually may be more involved than I first thought because of the single trigger wire to the radio. I am not even sure that I can do this (other than the using the single reverse camera). If incoming video triggers the camera video on the radio without the reverse trigger wire, I may be able to wire it up to each individual 12 on the turn signal, if not, I think that I will only get the backup via reverse.
Thanks again for the responses!