Exploring officers wore normal officer uniforms. They had to were uniforms or they would be executed as spies if caught by the French. There was one account of an exploring officer who was capture and then ended up having dinner with the French officers- all very civilised. Alas for his servant, a Spaniard, who was executed as a spy.
If I recall correctly initially Engineers was a normal officers uniform but reversed- so it was dark blue with red facing. Unfortunately this meant that a number of them where shot by their own side who mistook them for French officers, and so in the latter parts of the campaign they changed to were normal officers uniforms (ie Red Coat with blue facings).
You could always use the same figure as an exploring officer or an engineer
Edit- I gave you duff information there- the original Royal Engineers uniform was Blue with Blue facing- not red.
here is a picture...
And here is Major General Ross from the Sharp TV series
Note that Major General Ross has epilets on both sides as he is a staff officer- the other picture only has one epilet - this is what you want. I am going to use a victrix plastic officer I had left over form my line infantry- painted in this colour scheme.