This might have been better placed in the semi-auto forum.
That said...it all depends on what specific length, mfg, etc. you are looking for. There are multiple shops that come to mind with plenty of AR barrels in stock and ready to roll. Below are a few suggestions. Also, not questioning your call on the 1:9 twist as I'm sure you have your reasons, but you may be better served with a 1:8 unless you just have no plans to shoot any form of match/heavier weight ammo (i.e. - 70gr+).
Finally, check the equipment exchange on BARFCOM as you should be able to locate just about any barrel you'd like within a fairly short time over there.
WOA,BHW (My fav). I think RRA is 6+months behind, but they use Wilson brrls, and their 416ss brrls with WYLDE chamber shoots darn good. Pac-Nor (Noveske) is a very good brrl, and Wilson Combat also uses 416ss brrls.
I've read enough favorable things about Black Hole barrels to decide to give them a try. Haven't assembled everything yet, but by visual observation, it appears they do quality work.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Graham</div><div class="ubbcode-body">Brownells now carries WOA AR barrels in stock. </div></div>
I had the SPR rifle length and watch list and it was back in stock very quick and ordered. It's all about putting in some leg work, the joy of the hunt so to say