A good friend saved these clips (pics) from when he worked for GM. He kept them wanting to use them on his own project. Unfortunately he had to sell his Camaro. I used the ones that worked best for me, neither of which are like the originals.
The clip in your pic is obviously a re-pop but should work fine for the fender. The problem is, the original was not offset (look at pic) but how many people actually know this. This same offset will not work for the alternator bracket. by the time you attach it to the harness and tape it, it will be too bulky to penetrate/seat properly. And, no idea on where to get the clips. I checked for several days and the only one I could come up with is the one in your pic. If you find out, let me know.
As for the color, both of them should be white/off-white. But again, sure beats the heck out of buying the entire harness, and again...who really knows