Do you have a gas length preference? And would you consider a .223 wylde? Are you considering traveling or shipping? Or are you looking for only local? I'll have to check my parts bin but I'm pretty sure I have a mid-length 5.56 and a carbine length .223 wylde.
I found the BCA .223 wylde but it's an 18" barrel. I'm still looking for the other barrel I know is a 16". I'm pretty sure it's a generic Brownell's mid-length barrel. Let me know if the BCA barrel interests you at all and I'll PM you (what I would consider) a pretty tempting offer. If you aren't, I may list it in the marketplace.
https://www.bearcreekarsenal.com/b223wmhb1818-ssbwf