Beau Brummell: This Charming Man is a worthwhile video that slipped by me unnoticed until recently. The 2006 BBC television production is based on Ian Kelly's biography, and James Purefoy plays the Beau. The clothes are reasonably true to the times.
Watching it reminded me once again that one of Brummel's legacies (in addition to trousers, which he's arguably responsible for) is the day wear combination of a blue jacket, cream or tan waistcoat, white shirt, tan cavalry twill trousers and black half boots (the Italians didn't popularize brown shoes until later). Waistcoats and breeches were lighter in color than the jacket in those days, with the objective of giving a man a bit of the look of a marble statue.
A few parts of Brummell's look require a judgement call on a substitute that isn't outright costume. Jodhpur or chelsea boots would be the closest appropriate style, I think, to the original riding boots. And the contemporary equivalent to the Brummell's cravat would probably be a day ascot though I'm sure there are men who will feel they can't wear one (they should substitute a four in hand but they'll be the worse for it).
To this day, a blue blazer and tan cavalry twill trousers is common civilian garb in England, 200 years after the Beau wore the original clothes.