The tool Canvas Size also works for cropping - just make the canvas size smaller -, but requires a bit of fiddling and calculation, to make an arbitrary position cropping possible. First, you'll have to crop so that the anchor is in the top left corner so that:
- width = x position of the crop's top left corner + width of the crop
- height = y position of the crop's top left corner + height of the crop
After that, proceed on to make a second Canvas Size cropping, but now making the bottom right corner as the anchor and the width and height as the desired final size.
Another way is to use the normal Rectangular Marquee Tool and select Style: Fixed Size from the options panel (the one located by default under the menu bar) and setting the desired crop size. Now just position the marquee by holding on the mouse and adjusting it to the exact same position by reading the hover notification coordinates.