The CCTV camera I get from Harbor Freight.
I've used several on my house for security (connects right to the aux input of the television) and the resolution is very good. It's lasted for 5 years with no problem. The audio is good, too. You have to use a dab of silicone where the cable enters the housing (which is sealed and gasketed), the grommet isn't sufficient to prevent fogging. It runs on 12 volts DC, one power, one negative, one audio, and one video. The factory uses a 4 conductor phone cable, which works fine. I modified mine to plug into a standard phone jack for ease of installation, since the distance was further than the supplied 50' cable.
I installed one one my 1970 Mowhawk Honorbuilt trailer, and it works fine.
These cameras are far better than the old junky ones they used to sell.
The 3.5" LCD monitor I ordered on EBAY (Part #220871253052) from Hong Kong. $25 and free delivery. Sorry, but I can't even get an Amercian company to return my phone calls for less than $25. Too bad, really.
The LCD displays usually last only a year or two, but for $25, I can afford that every couple years. It plugs right into the cigarette lighter. You'll have to do a little wiring and routing to get the wires from the trailer to the cab of the TV, but that isn't too hard.
I plan on using a toggle switch to select the video feed (One camera will be pointed directly down to the tow-ball/hitch, so I can hook up solo, the other camera will be on the trailer, mounted above the bathroom window.) I can route the wires through the vanity cabinet, along the inside of the trailer, to the front connector.
I'll be posting pics pretty soon of the "Aerojava" trailer. It's almost ready.