This seems to be misbehaving on my ATV (this has a 3 cylinder diesel, badged Caterpillar but presumably Japanese, and has a "glow plug on" light). From a quick eBay, I can get one for a Freelander for £15. There's a separate relay on the engine to switch the glowplug current, I can't see any obvious reason why a Freelander timer should not work. (Obviously, I may have to fiddle with the terminals but I have a workshop manual for the ATV so it's easy to work out the connections)-.
I did just wonder whether to fit a manual switch, perhaps a "spring off" one