B&H has the JVC GY-HM170 and GY-HM200 4K camcorders in stock and now shipping. Both models capture 4K video at 24p or 30p at up to 150Mbps and 4:2:2 1080p video up to 60fps at 50Mbps.

The JVC GY-HM170 can be found here at B&H Photo. The GY-HM200 includes a shotgun mic and carry handle with two XLR inputs and can be found here at B&H Photo.