Of the top of my head I believe Vltor and Rainier Arms have an upper which has a Dust Cover or Ejection Port Door Cover and without a Forward Assist. I am sure there are some others.
The Constitution is not an instrument for the Government to restrain the people. It is an instrument for the people to restrain the Government!
“Americans have the right and advantage of being armed. Unlike the people of other countries, whose leaders are afraid to trust them with arms.”
James Madison. Author of the 2nd Amendment