HTC Desire HD : Need Lock Screen App

I want to turn off the screen and lock the phone fairly often, and am getting fed up with groping for the power button on the top. I am also worried that, over time and regular use, it will stop working. I am looking for a simple application that will do it for me - at least turn it off, I suspect that turning on will be more of a challenge. Has anyone found a simple one that will do that for me - all the ones that ought to do it on the Market seem to be very complicated with lock screens and skins and so on