These aren't (yet) the correct, single D1 setup, but you could always "shorten" them down by removing two of the lamps and trimming the width of the center housing down before re-imstalling the end cap. Not a bad idea if you need the Federals, cuz you CAN'T get them anywhere.
http://www.ebay.com/itm/FEDERAL-SIGN...9e3561&vxp=mtr