The Megabot was shown on the Winter 1987 and February 1988 Rogue Trader part 1 flyers. It exists both as a one piece casting with the tab reading Megabot and a two piece casting using the same legs as the Roborgs.
Sculptor:
Bob Olley
Painter:
Andrew Taylor
Iron Claw Megabot & Squat Hovercar
RT1 Flyer (February 1988)
Iron Claw Megabot