Off-colour Max/min thermometer

After 4 years my max/min thermometer is almost impossible to read because the blue dye in the liquid column has faded away almost to nothing.
It's not branded but has a patent number in the bottom left-hand corner and 'Made in England' in the bottom right (bless!  )

Can anyone recommend one which doesn't fade (red rather than blue possibly?) - I'd consider a digital one although in my experience sub-zero temperatures and batteries are not a happy combination. 

Thanks Lardman - as part of my basic weather station I do have a remote temperature sensor which I originally placed in the GH, but now use it with its plug-in sensor dangling outside so the unit itself can stay nice and warm in the house (it didn't work reliably in the GH, but that could have been its transmission range rather than the batteries.)

There are a surprising number to choose from 'out there'  and it's not quite my birthday yet, so no rush.