Where can I find nice larger-sized mens dress shirts?
Sounds like you need a big & tall store. My husband buys dress clothes from Rochester Big & Tall, which a quick look tells me carries Ike Behar shirts (as recommended) in the size you mention. I’ve bought clothes from them in several different locations, although I’ve never purchased online, and their customer service has always been top-notch. We’ve never had trouble with returns, including things sent by out-of-state relatives as Christmas/birthday gifts. I have no commercial connection with Rochester; they just know how to make a big/tall guy (my husband is 6’4″ and built like a Viking) look really sharp in nice clothes.