When in the 1800s? Toff would be the perfect choice here, but it isn't found any earlier than 1851, and I would be shy of putting it into the speech of anyone until at least 1855 (maybe a bit braver if they were in the Midlands, East or South East of England).
After that though, it would be a common word that matches your description perfectly.
(It's still in use, but not as much as before, having peaked in the first half of the 20th century).
Edit: Comment says this is set in the very beginning of the 19th century. That rules out toff and even haw-haw (around 1825), and beerage is right-out (1880s).
His nibs is an interesting example, but just too late (first attested 1821).
You could take a punt on haw-haw and his nibs on the basis that the first spoken use is likely slightly earlier than the first printed, but it would be a stretch.
Nob is an interesting one and might be apt. It's often understood as a contraction of noble, but while that's probably an influence, white-knob also spelled white-nob is found in the late 18th century until early 19th meaning an upper- or upper-middle class person in reference to the white wigs they would wear and it got contracted to nob. Hob-nob was likely also a further interest.
In any case, nob hits your meaning and was in use in your time, and white-knob also hits it, was in use, and has firmly died-out since, so it might be favoured as giving more temporal flavour.