Your best bet is to run them through a relay so that they only turn on when the car is running.
Also how much have you looked behind that bumper. A good amount of cars will have the wiring there anyway even if it isn't originally equipped, its cheaper to design and build one wire harness with a bunch of plugs than it is to design a bunch for each individual option available. You might have to look at a wire diagram or a car specific forum to see if they have the plug already or not.
Just as an example my old ford focus came with 3 speed wipers, and to change it to the 10 speed/infinitely variable wiper, all I ad to do was change out the switch. It also came without power locks or windows and all I did was wait for someone to wreck their car and bought the necessary switches, parts and plugs from them. but all the wires were in place.
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