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!
If the Freedom of Speech is taken away then dumb & silent, we may be led like sheep to the slaughter!