As far as I know, House of Blades is it. You might go there, but if you do, make VERY sure you get the owners wife, a very nice oriental lady, to do the deed. She or maybe their son, are the ONLY persons there that I'd trust, and not a lot...
A long time ago, I bought a SOG there. As you might know, if you buy a knife there, you get free lifetime knife sharpening. I let their guy do it. He, using a belt sander, ground a good part of the thumblug away. A friend of mine, let them sharpen his Tanto blade. They botched it big time. BEWARE!
Check out my post to Mick regarding the optimum sharpening angle for ARs. I use either an Edge Pro Apex &/or a Spiderco Sharpmaker. I'd highly recommend the Edge Pro. It's almost fool proof. I'd be glad to help you sharpen your AR the first time.
BTW, that's not really me in my new avatar. That's just how I'll feel until I finally get my very own AR...