Laser collimators are easy to collimate themselves. I took a piece of flat wood, and drove 2 nails into a V pattern on one end and 2 more nails in a V pattern at the other end. Then just sit the laser in the little cradle you just made, turn the laser on, point it at a wall, and rotate the tube. If the dot stays in the same place, congrats it's collimated! If it moves, then adjust it.
I bought this SVBONY laser collimator last year, didn't need collimating but I still checked it.
It's a 12" f/5 dob. I'm using the adapter from this laser collimator (which I suspect is too tall.)