You can find the Nordic 22RB Complete Upper .22LR 16" here.

The Nordic Components 22RB dedicated upper receiver converts your standard AR-pattern lower to a dedicated .22LR for recreational shooting, training, and hunting. The 22RB is manufactured using the same materials as standard AR-15 rifles, ensuring it looks and feels like a centerfire rifle. The 22RB's match-grade barrel also comes prepared to accept a suppressor with barrel threads cut to the proper spec for most popular .22 suppressors, and a mortise to accommodate the O-rings found on certain suppressor models is machined behind the threads. Includes 10-round Black Dog magazine. Will accept all Black Dog AR-15 .22 magazines.