Armalite AR-10A4 B series upper options

[Rparrish]

Hello, just curious if there are any options for using any other manufacturer's A4 style flat top upper receiver on a B series AR-10. I would prefer to use an Armalite upper receiver,  but it's rather difficult finding one at this point. Any help would be greatly appreciated. 

[jtallen83]

NOT Matrix, they have a similar looking cut at the rear but the two I have, one with DPMS barrel nut threads and one with Armalite barrel nut threads, will not interchange with my B model Armalite. I am not aware of any currently on the market that will swap.