The earliest touch-ups I did to that car were over 20 years ago, and they still look good, so durability is not a problem. I think the key is to keep the area small and blend it well; at least, that's what I did. I also prepped it thoroughly rather than just try to fill in the chip.

I'm sure you're right about powder coating, but that's out of the question.

My wife and I just joined a local car club, so I can ask my fellow members for a paint shop who might be able to mix a small batch for me. Also, match the unknown (by make, etc.) paint color as suggested here.

Thanks for all of your help and advice.
Dorsey