Does anyone know where I can get a Land Rover Defender battery cut-off key?

I only have one for my Land Rover Defender 90, and I need a second one really, but have no idea where to get one. The type I have is a red plastic key that goes under the passenger seat. Anyone know where I can order another?|||a local locksmith should have keys for a 90 land rover, it uses the same key blanks as fiat cars 62ft and 62fs if you want to call the locksmith ahead of time ask if he has either of those two key blanks in stock.