From experience, it appears that no-one makes an aftermarket pole clip for the hobbiest builder, at least not available in the States. With 99+% of the tent manufacture being done overseas, most of that specialty small hardware like that never makes it to the states. There probably just isn't the demand for it, other wise you would folks like Quest or OWF carrying them.
You could try contacting DAC or Yunan to see if you could buy some of their clips (I don't believe Easton makes any of their own pole clips). The problem might be that they would want you to buy a case, which may mean a few thousand clips. A small side business perhaps?