Your gun of course. mine was a Taurus Model 970 Taurus USA
8" Black Multi Color Wraps Strap from [http://www.radioshack.com Radioshack] Product Catalog 278-1676 $2.99
or any strap you can get/find.
35mW Green Laser pointer from techlasers.com $99 Infiniti Green Laser Pointer
You can get the higher wattage version from their site. The higher the wattage the meaner the pointer in looks.
Step 1: Of Course You Need the Laser I Bought Mine From Techlasers
Step 2: This Is What the Wire Strap Look Like
Step 3: The Gun With the Laser Hehehe Accurate As Far As You Can See :-D
You can also used another wrap as long as it can hold your laser tightly.
Packing tape maybe :-)
Adjust the laser until you can see thats its straight enough or the dot is right on the target.