Never seen one. All the ones I've seen want to mount to a box. You could surface mount a (weatherproof) box behind it.

See below

Here is a link that might be useful: Adjustable Motion Sensors

Thanks, but those all need J-boxes. I'm looking for something that doesn't need that, but has the j-box built in.

Read section 2 below

Here is a link that might be useful: Installation instructions

Thanks, certainly something to look at, guess I should have looked further!

Keep in mind that you can get a very shallow box.