My version :-)
Based on Mike's (of
Mikesworkshop) design , I've pared this down to the minimum using a plastic body and automatic centrifugal switch.
Photo 2 - The cap is sized and shaped to clip into the 21mm battery recess
Photo 3 - the cheap 50p eBay laser module has the wires removed and a 40mm piece of tinned copper wire added to the negative (resister) terminal - the module's PCB has to be trimmed (grinder) to make sure the module will press nicely into the 6mm hole
4 & 5 - Once the module is pushed home the wire can be bent around to form the Negative battery connection. A small piece of plastic foam packing is used to push the 3V lithium cell away from the laser body (the +ve connection).
6 - Once the thing is rotating above a couple of hundred rpm , the battery is pushed against the body of the laser module and it lights up.