I followed the advice below from the CMP forum ...
"U.S. GI clips are fine for display purposes, but not for actual use. The tabs break off of the springs and the springs come adrift after one or two uses. They were designed for single use only.
Swedish Mauser clips work very well and are still available in large numbers at reasonable prices. SAMCO has them on sealed boxes of 40 for $14, or you can buy in much larger quantities.
South American 7mm Mauser clips fit perfectly and don't have tabs. they are reliable and durable."
As of last fall Samco still had cases of 40, NIB with minor tarnish from storage - work fine. I don't see them on their site right now but they might be worth a call.
You can find the Swedish Mauser clips at a few sites and on Gunbroker, but a lot more expensive than the Samco pricing.
/Bryan