You can't go lighter with a blow-back pistol because the only thing keeping the slide shut during firing is the mass of the slide and the weight of the recoil spring.
Go any lighter and it gets unsafe fast.
One trick is to build a "cocking shelf".
This can be as simple as a piece of brass or copper pipe that will fit over the muzzle of the barrel and will clean the frame on the bottom.
Mount the pipe to a wood board and mount it firmly on any handy surface or wall.
To use, simply grip the gun tightly and push the muzzle onto the pipe, then pull the gun back. This will force the slide back, cocking the gun and chambering a round.
If the gun has a slide stop, put an empty magazine in the gun and use the cocking shelf to lock the slide back. Then insert a loaded magazine and lower the slide.