He's hiding in the background of William Sidney Mount's Rustic Dance After A Sleigh Ride. The suit is damn fresh, but check out the pleats in those trousers. Early 19th century fashion went bonkers with trousers. There were tight, lower-calf hugging Pantaloons, Moschettos with feet or shoe tops like overalls. Breeches were still worn for dress occasions, but hipsters wore long pants.
Alexander I brought Cossack dress to London and the result was ridiculous. Think MC Hammer with stirrups. The remarkable number of these that survive in museum collections may indicate how embarrassed their wearers were after one outing in them. Our hero appears to be wearing a less baggy version.
Holy hell. There might just be enough checked material left, but only if the legs are a reasonable dimension. The pleats might make the wearer look less frog-like. Since the coat turned out well, let's go back to Laughing Moon for the pattern. It includes most waist sizes for all the different crazy trouser patterns from the period, even a cord pattern for Pantaloon Trousers.
Remember the yellow trousers are too short on top and only come down to the ankles. Adding two inches to the top and three to the bottom solves both problems. Hopefully the stirrups will last awhile since they ride on the instep.