I made my own for about $25 out of a mirror and a Daisy laser scope for an air pistol from Walmart. The scope has axis adjustments for the beam and a nice stable base. The trick is to aim it at the mirror and rotate the scope and adjust it so the reflected dot does not move. Then you can be sure that the beam is perpendicular to the base. Then simply adjust the enlarger until the reflected beam hits the source. Sounds more complicated than it really was. Now my enlargements are nice and sharp - corner to corner.