D'Addario make a set of flat wound 12s with a wound third.
They have a 13-56 set too.
― EZ Snappin, Monday, 20 August 2018 20:49 (three years ago) link
I gotta try flats sometime, suspect I will never go back
― an incoherent crustacean (MatthewK), Monday, 20 August 2018 20:51 (three years ago) link
If you don't want flats they make a nickel round wound set of 12s with a wound third (12/16/24w/32/42/52); I use them for my slide setup. Look for their jazz strings.
― EZ Snappin, Monday, 20 August 2018 20:53 (three years ago) link
The Half Rounds I put on my Duo-Sonic have a wound third. They're really good strings. I may have found a new favorite.
I'd like to try the Thomastik-Infeld flatwounds, but jeez, that price tag!
― outside, you're never alone. (Austin), Tuesday, 21 August 2018 16:25 (three years ago) link