I stongly believe in using a bright Tactical light and Laser for a HD shotgun. The tactical light not only lets you see but needs to be bright enough to blind anyone looking in your direction. Of course the Laser is to get you on your mark as quick as possible regardless of if you have your gun shouldered or are shooting from the hip.
A lot of cheap lights and lasers advertise for shotguns but are really only good for air (airsoft) guns as they do not hold up to the recoil. I have a Mossy 500 with a picatinny rail that bolts to the reciever ($10). I then purchased the osprey 6132 laser rail mount for about $50. There where a number of reviews stating that it handled recoil well but I found it extremely difficult to adjust. When you start tightening an adjusment screw the beam will go one way for a while then start moving in the opposite direction, trying to adjust with the opposite adj screw just makes it worse. After 45 miniutes the best I got was an inch from the bore sight at 30 feet.
For the Tactical light I picked up a firefield model FF21001K which came with a barrel mount for about $40. The light seems very good but the mount is terrible. Finally I got a good Brownells light mount spec'd for a 1" light for $34. The Firefield is listed as 1" but is actually a bit larger so I had to do some mods to make it work. Ok so $134 for something that should hold up. 120 lumens on the light with a red laser adjusted close enough for HD.
Earlier I purchased a shotgun laser for $14 with a barrel mount. the mount was ok and the laser adjusted was not to bad, had it zeroed in about 20 minutes. Later reviews on it said it did not hold up to recoil. Deceided not to bet my life on it.
Let me know what solutions you have come up with for your HD shotgun .