This is a very simple printhead for the Ultimaker 2, which was designed to mount one of the very cheap and common lasers from china. It is very easy to print and versatile.

You'll need two bearings to slide on the x/y rods (for the ultimaker 2 those are ø6mm on the inside and ø12mm on the outside (part is often called LM6LUU or LML6UU). You can take these out of your existing printhead (inconvenient) or find them online starting around 4$/pair. Also you'll need ø3mm screws at least 50mm long (depending on what you want to mount etc). These can be found in any home improvement store or online for less than 2$/10pieces.

Note: the screwDistance variable in the scad file does nothing right now!