The best one I've ever had was from LL Bean.
yep. bean or lands' end.
You need to start looking for whatever brand puts the shirts out in proper sizes. In the uS, that would be 15x33, 12-1/2 x 34, etc. Collar x sleeve length. Buying shirts sized in the S-M-L-XL format is a crapshoot as far as fit is concerned.
Your not going to find that for flannel shirts only dress shirts.
Pendleton is a brand I have used for years, but until recently I have not seen flannel shirts on their website. If they happened to stop producing them, I would advise looking at thrift shops.
I also posted this question in the Intro section by mistake and received this reply:
Pendleton makes some fine flannel shirts:
If you're on a tighter budget, I saw some nice ones this afternoon at Sears.
Buckle down and buy a wool Pendleton shirt. They're life-long investments. I own some from the early 70s!