I think you can use knife edge method to measure the size of the spot of a laser Emmanuel Vincent Péan

Stuck bead method also can be used to determine the laser spot size. Following paper may be helpful.

http://penerbit.uthm.edu.my/ojs/index.php/JST/article/download/2058/1302

It depends how precisely you need to measure.

Here are some ideas you can try.

You can use a single mode fiber with a 9um core and send the light into a power meter. Scan the fiber on a translation stage and record values and then do a fit to the data.

Or, just shine the laser at a piece of paper with some kind of graduations for knowing the scale and then take a picture from the back side of the paper. Use the scales in the picture to calibrate. This will have some error due to scattering and fluorescence. Take the picture with your cell phone and a macro lens attachment, or a microscope if you have one.

Or, shine the laser on a flat surface at a very steep glancing angle. Measure the length of the streak on the surface and use your known angle to calculate. An infinitely small point would have no streak.

It does not need a special "Laser CCD" camera, almost any CCD camera with a strong ND filter can be used as long as you know the pixel size. For a beam with a diameter in the mm range it is most convenient. Fit a gaussian profile in the exported image with a math program of your choice.

May be one of the best methods is to let the laser beam falling in a camera and take a shot to build the image of the beam. This image can ten be displayed on the screen and the size of the spot measured.

Best wishes