This was a legitimately hard question to answer. I searched all over and only came up with one solution for you: Pendleton. Probably going to want to size down one, maybe even two.
ADDING: Also maybe Noluur? I just found them via a Google image search. No idea on their quality, etc.
ADDING from dieworkwear replied:
Pendleton fits huge. Try John Smedley, Club Monaco and J Crew
I couldn’t find one from J.Crew that was in brown.
ADDING: transparentstyle replied:
He could try L.L. Bean’s lambswool cardigan. I have one and I love it. The closest thing to brown is the “dark camel” color. Cheers!
I noticed that one, but was looking for more “UPS” brown. Still, it’s an option and pretty affordable.