OK as was suggested in the response to my original post, I am attaching a photo showing the open battery compartment on the back of the bass, the original cover (which has lost the clip to attach itself) next to it, and next to that is the only kind of battery compartment lids that seem to be available on ebay. (I have ordered two now from separate sellers, and they are both exactly the same). The distance between the screw-holes in the original is 4 cm by 3 cm whereas the distance between screw holes in the replacement is 6 1/2 cm by 3 cm.