I didn't know that Cinematic Precision sold Bridge Plate Adapters as well. Do you have a link?
http://www.arri.com/camera/pro_camera_accessories/support_systems/bridge_plates_bp_12_and_bp_13.html
Should this be a sufficient replacement to the BPA-1? I think that this is just an updated version of the BPA-1, to allow the use of the Alexa shoulder pad.