Thermometer

I have the Lunar campercar that is built on the NV200 but as far as I can see it has no thermometer to indicate outside temperature as an ice warning. Every car I've had for the last 20 years has had one as it costs the manufacturer peanuts to add. The display is usually on the radio but on the NV200 the onboard computer display could have been used. If there really is not one on the NV200 to fit one myself is a great deal of hassel. Thinking of one of those indoor/outdoor battery powered thermometers unless any one else has a better idea. Thanks.