I bought everything from Halfords, a dutch chain store with excellent stock for all vehicles; cars and bicycles.
For a rack back light, there are many options, including a light that turns on automatically when it is dark, or one that will flash at the push of a remote button to help locate your bicycle. I choose the simple one with a shape that will allow me to slip the pannier hooks under it.
My touring bicycle does not have back brake bosses so the lock must be attached to the seat stays with the provided slips of sharp aluminum. The instructions for installation are miniaturized to the point of incomprehensibility. I had to choose Optie B.
The warning should read "DANGER! Strips are sharp razor blades designed to slice your fingers."