I have
this one. bought it on sale a year or so ago... really like that I can see what's behind me heading down the road and is almost a necessity for backing in site when I travel alone.
I had dealer install. He suggested hooking to "hot wire" for light just inside rear of TT. Wiring is connected in cabinet so not exposed and ugly in trailer. by installing this way it works even if I don't have trailer lights on. just be sure and put a fuse or switch in the line or it will pull power all the time.