If you want a permanent mount, use this 3M stuff. People use it to, among other things, stick decorative accents to car body panels. It's holding on the front license plate of my car. As the picture indicates, it's good enough to stick objects even to porous materials like brick.
https://www.amazon.com/Scotch-Exterior-Mounting-1-Inch-60-Inch/dp/B00004Z4BV
It's got a foam cushion backing so the power strip won't sit flush on your desk, if that will be an issue. It *can* be removed with solvent and a butter knife, but you're gonna have to work for it. If you're not careful, it'll peel the paint or varnish right off the desk. The only issue I can think of might be temperature, if the part of the power strip you're sticking it to gets really hot.