I've designed a mount for the following laser I bought from Aliexpress:
https://www.aliexpress.com/item/500mw-405NM-focusing-blue-purple-laser-module-laser-engraving-TTL-module-500mw-laser-tube-Laser-module/32562052620.html

newer version now supported another popular module as well!

I've made it because all the other designs I found required me to removed the entire carriage and and reattach the belts. With this design you only need to remove the cooling fan.

Update 08/11/2017:

I modified the model a bit in order to fit another popular laser module:
https://www.banggood.com/445nm-2_5W-2500mW-Blue-Laser-Module-With-Heatsink-For-DIY-Laser-Cutter-Engraver-p-993521.html

I haven't tested it it but when I do I will update with new video and pictures.

Original file: laser_mount_anet_a8.stl
New version: laser_mount_anet_a8_1.1v.stl

• The new version supports both modules, I recommend printing this one.

Video:
https://www.youtube.com/watch?v=j7RHM9WuDvk

DISCLAIMER:
WORKING WITH LASER IS EXTREMELY DANGEROUS. MAKE SURE YOU FOLLOW ALL THE PRECAUTIONS FOR WORKING WITH LASERS, WEAR THE GLASSES RELEVANT FOR THE LASER'S WAVELENGTH, ETC.
YOU CAN VERY EASILY BLIND YOURSELF AND OTHERS OR EVEN BURN DOWN YOUR HOUSE!