From Lord Rockwell, the Not-A-Bumpstock stock.

...We're letting the market know an alternative product exists. The Not-A-Bumpstocks are a more complex system. More than just replacing a grip and stock. The Not-A-Bumpstocks will be available as conversions kits for existing firearms and as complete firearms with an integral Not-A-Bumpstock. More details on the operation, safety, and availability of Not-A-Bumpstocks will follow after Christmas....