I have come up with a solution for the 2-wire Heath power cords like used on the SB-301 and SB-401. This solution uses a 3-wire cord with push on connectors for the "hot" and "neutral" with a terminal lug that attaches to the ground lug on the unit.
Details at:
http://k9sth.com/uploads/Heathkit_Power_Cords.pdf
Glen, K9STH
Website: http://k9sth.com