there haven't been any deals on flat-tops in a while. every once in a while some deals will come around of surplus a1 and a2 uppers.
a long time ago LAR would have blems on sale for $60 but i think they have a back order list 20 miles long now.
BCM has had some for a bit more that are used. i think they come with the port door and forward assist installed for about $79 IIRC.