Balanced Grounding Pins

I have a Krell amp that has both balanced and unbalanced connections. When not using the balanced connections, you have to install a U-shaped grounding pin or you get hum in those channels. The amp came (used) without the grounding pins, and I want to find some replacements. Anyone know if these are unique to Krell (I can't imagine) and if not where they can be purchased? I went to some local stores and they looked at me like I was from Mars.