Since I got my Yashica camera I tried multiple ways to adopt a px28a 6v battery (also known as 4LR44, A544, K28A, V34PX ), first with aluminum foil, then with all kinds of metal pieces. The result was inconsistent and unreliable. The most frustrating part was when the film was developed and the film was underexposed with no salvageable frames. The camera without the battery defaults to 1/500 speed which is ok for outside shooting but limited for indoor situations. The adapter is simple but reliable just slide a px28a 6v battery and you are good to go.

This adapter is also compatible with all Yashica Electro 35 models. 

The listing is for the adapter only battery not included.

Happy Shooting!