Got these photos from Jason, Gunsmith at Epps. I sent him a drawing of something I would want for my SR22 rimfire, he told me he made one that was just about the same as mine but with a 8" OAL for a .223 AR.
As for pricing, I imagine that cost would be different for each one as per your own specs.
This is his ... designed to slip over the barrel and not add too much length to your current set up.