Not sure what bulb you would have in your panel – I haven’t got a battery charger warning light on mine (unless you mean the low voltage light?)!
Can you remove the bulb and wander down to Halfords with it? If they haven’t got one they can probably advise where you might get one (Maplins possibly?).
Hi Rog, got the wrong end of the stick so to speak, am looking for a replacement bulb to show connected to shore power, the battery warning light to show the battery is being charged is part of a printed circuit so will forget that one.