Hand engraving

[ven]

I am making a brass analemma, a sort of sundial, and I have discovered that the small spot of sunlight doesn't show up very well on the brass face once it has discoloured and darkened.
Can anyone tell me where in the UK I can buy a piece (about A3 size) of weather-proof plastic sheet - the sort that is used for door labels and is about 3mm thick.  I would want a sandwich of two colours so that I can hand-cut through the lighter one down to, say. black or dark grey.
Thanks

[DaveH]

Ven,

This may help.

http://www.gravograph.co.uk/
 
DaveH

[DMIOM]

Ven,

in case it helps your search, the trade name for the original laminate was Traffolyte (though sometimes mis-spelt as Traffolite)

Dave

[ven]

Many thanks for the replies. Traffo-whichever is just the stuff that I was searching for. And a helpful reply from a foreign land, within minutes - wonderful.