Adding an on/off switch

I posted before about my problem finding sconces with on/off switches and I'm back again. To recap- i just bought an old house with 9 wall sconces- but none will turn off. They are not attaches to a switch and they do not have pull cords. The last person installed outside wall sconces that just stay on all the time- only way to turn off the light is to unscrew the bulb. The walls are plaster so I'd rather not install switches. I want to find sconces with on/ switches so I can just replace the light and be able to turn it off and on- but they are very hard to find!

I tried to find some kind of thing that you can screw into the socket to add a pull chain to the lights currently there- and then the lightbulb would screw into it. I can't find any such thing. They have these "daylight timers" that work kind of like that- but I don't need a timer and those are very bulky so the lightbulb would stick out. Help!I just want to turn the dang things off! I have burned my hand too many time unscrewing these blasted light bulbs.

Is there a way to add a switch to a sconce that has no switch? or is there a product such as the one i attempted to describe above- that can put a pull cord on a light bulb?