I can't afford a Versalab Parallel.. but there are these rifle boresight laser alignment tools.. basically a cartridge with a laser pointer built in.
I'd imaging the 12 gauge one would work particularly well, just rest it with the laser pointing upwards, place a mirror in your carrier, etc..
Easier than building a laser diode driver for one of those cheapies, easier than mounting a laser diode perfectly 90deg. to your baseboard, etc.
Cheap (from China) on the *bay*.. just a thought.