Well i looked for a long time on internet but was unable to get any information on how to run a 4.5v laser on mains .
So I decided to make it myself as for laser alarms it is good to have a laser run on mains.

Step 1: Material Required

Laser
Switch
Portable USB charger (don't go for expensive one I used one of ₹35 )
Tape
Colour
Cutter

Step 2: Cutting Laser

Cut the laser in such a way that you get the back spring out .
Scratch out the outer colour of laser
Soldier one wire to upper leg of the push button and one to the scratch metal area

Step 3: Body

I made the body out of electric wire holder used in house wiring .

Step 4: Charger

Take out all the material inside the USB charger and attached a USB lead to it.
Cut the lead and take out red and black wire . connect black wire to negative wire of laser and positive to switch attach other wire of switch to positive of laser.
Attach the wire out to main from charger to a two pin a fit all the components within casing .

Step 5: Colour

Colour the charger and run the laser on mains.
Go for your home security whole night without thinking of changing cells but save electricity switch during day.
Thanks and give nice comments.

Step 6: Update

well i used a PVC pipe for making body after few days of instructable . i drilled a hole in front of size of laser pointer.
well that all in the update and if you like it then comment.
i will keep bringing new unique instructables in future.