M7 is found on motorcycles, scooters and pushbikes, rarely long stuff though, usually 25mm for holding ignition rotors and similar stuff.
M7 is 1mm pitch, so is M6, try fitting a 6mm helicoil and using an M6 hex bolt, 70mm length is available. Seeing as it is only a stock bolt M6 will be strong enough, fit the helicoil correctly and again it will be strong enough, I would suggest using a 1.5D length, you will need to run a 1/4" drill down the existing M7 thread, seeing as it is 1mm pitch the helicoil tap will run in very easily as you will only be cutting a few thou with the tap. You may need a washer as the M6 hex head will be smaller than the M7 one you are replacing.