Here is an inexpensive Laser Edge Finder that is cordless. It could be made using a USB cable for power but I wanted a cord free design. The parts are very inexpensive on eBay. The key chain flashlight is $1 and the Laser Cross Hair is about $3.50. Just turn the arbor concentric and make it a slip fit for the laser assembly.
I used CA glue to fasten the flashlight to the arbor and put a very small drop on the laser itself at the very end of the arbor. The flashlight was disassembled and the led removed but the led mounting plate was used for the connector insulator. I just tinned the laser leads and bent them over using that insulator for the new connector block. Works fine every time. The "lens" on the laser is adjustable and the thread was very loose which made for a very inaccurate unit. To snug it up I used two wraps of teflon tape (plumbers variety) on the threads and now it is much better. If you are looking for .001" accuracy and a very fine pair of cross hairs you should invest in a laser that is of higher quality. This one works fine for a quick setup but I still go to my mechanical edge finder when I need .001" accuracy. One of these days I may find a better laser crosshair.
The steel used was just HRS. It was 3" long and 1" in diameter. Od was turned to .875" which made it easy to hold in my 5C collet square block for drilling the side access hole. I think that was .500" which gave the flashlight just about .015" clearance and some room for glue. The hole was step drilled and finished with a .5" EM. I was careful to leave a step inside for the end of the flashlight to register on. The hole for the laser finder was drilled as deep as I could go to allow room for the excess wire of the laser cross hair.
The flashlight is only $1.00 on the bay so I bought several and gave my wife one for her purse. One of the 4 that I bought would not operate due to a bad switch. Not all that bad for $1.00