Buy a new clock movement from eBay. Priced at £1, they come from China, You need the longer spindle type, so search long spindle clock repair movement. Might cost up to £1.50. Just unscrew the old mechanism, screw on the new ones & fit a battery. To prevent water getting in, I bought a silicone soap-mould for 59p from eBay, & taped it over the movement on the back. Works great.
Little Bren
July 2017