Have you seen the one by Frontline?
Its a RHA crew, 4 gunners and an officer, and looks OK from the image on thier website.
Also Alexanders Toy Soldiers
http://www.ats-uk.net/ has on too, painted is his gloss finish, but sells the castings so can be painted in matt if required. He only shows us a 3 man crew, but other poses from RHA could be added
The All The Kings Men has recently released its Rocket and crew, but they are in RA uniform, so suited to 1812.
And finally Barzso has a plastic set from its 1812 series.
So there..... do we really need more Napoleonic Rocket Artillery????
Of course.... but I'd love Royal Artillery and French Line Artillery (Horse and Foot) in preference, then French Arillery of the Imperial Guard, Prussian Artillery ..........
Regards,
John