I have an 06 F150 that was my Dad's. I can't see to backup!

So I've received the wireless backup camera today. It has a monitor that goes on the dash. I'm thinking I might wire it to the light inside the topper? I think that is hot all the time tho, because it works when the truck is off. I don't want to run the battery down so will I have to run power to a tail light? I'm planning to mount at the top of the glass on the back of the topper. I looked for a new stereo for the dash.. With backup camera included (all we have available here is Best Buy). They have expensive head units but adding an actual camera would be almost $300 additional which seems ridiculous. Does anyone know if I can wire to that power going to the topper light? If there is a reverse wire can I still make that work?