The 1st photo shows an original pump and clip. I should be easy to cut a hole in the pump with a Dremel tool. It may be wise to remove the cover before you cut into it. It should also be not too difficult to make a retainer clip similar to the original clip.
The 2nd photo shows two original pumps. The one without the hole would be for the washer system with the vacuum foot pump. That bag was not attached thus there is nothing hanging from the bottom of the bag to accept a clip.
The 3rd photo shows what the foot operated vacuum pump bag and cap looks like . There is no motor for this system. a hose goes right into the top of the cap and then feeds to the washer nipples.
The 4th photo shows the components of the washer system with the electric pump. In the photo the bottom of the bag is folder under so you can see the gromet to accept the clip.
Charlie Valentine