WANTED: Food thermometer (Romiley SK6)

Food thermometer
WANTED
Food thermometer
Romiley SK6
DESCRIPTION
Hi I'm looking for a cooking thermometer as my child is trying to make cinder toffee successfully but it keeps failing to set! Apparently temperature (300 degrees) is very important. If anyone has one they don't use anymore, I'd be very grateful. We're on our second failed batch and the kitchen is foggy with disappointment! Thanks for reading.