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!
A Government that abrogates any of the Bill of Rights with or without majoritarian approval. Forever acts illegitmately, becomes Tyrannical and loses the moral right to Govern!