I have found countless threads dating back to 2001 on this topic of the phantom part that seems to be not available to purchase. Whether you own a Mazda protégé, a street bike or anything else involving this part # and a H7 headlight bulb... look no further. Link follows..

https://www.rockauto.com/catalog/moreinfo.php?pk=3387438&cc=1387447

This little part ( STANLEY SN911-01200 adapter socket ) caused me way too much time and more money then I would like to admit. I had to leave this in hopes the next fella searching this part will come across this and save him some grief.
Cheers from Van Island, Can

STANLEY SN911-01200 adapter socket holder h7 headlight