Does anyone know what size, or indeed where I can buy a replacement screw for a 1/2" ratchet?
Obviously I can buy a full repair kit which will come with 2 of them but other than missing one screw that has got lost the ratchet is perfect.
You do not even need to take it out - turn the ratchet upside down and try an M6 screw in the hole in the lower plate, or an M5, or an M4.
Probably easier to find a socket countersunk (allen key) than a philips head as the replacement.
You will end up buying two so the heads match or it will annoy you every time you look at it. Tiny dab of loctite or superglue will stop the new ones coming out.