Yes! If you Google "Brownells Two Piece AR Gas Block". You will see they have a couple of styles. They attach with four hex screws. The one I have has the Picatinny Rail on the top and the bottom. But they also have on with the Picatinny Rail on the top and Bayonet Lug on the bottom.
The Constitution is not an instrument for the Government to restrain the people. It is an instrument for the people to restrain the Government!
Today, we need a nation of Minutemen, citizens who are not only prepared to take arms, but citizens who regard the preservation of freedom as the basic purpose of their daily life and who are willing to consciously work and sacrifice for that freedom."
-- John F. Kennedy