Hey guys I'm trying to find the last piece for this beauty. She's all original even down to the hoses. I've been searching swap meets and Facebook groups and eBay with no luck! If anyone has any leads or knows who might have this little piece laying around I'd be grateful.

try E-BAY think I seen one on not to long ago

You can make these from extra trim, Dremel, JB weld and determination.   I made similar parts for a 64 Fairlane wagon gascaps that has rare trims. and about 15 years later they are still on the car.

Go to the Home page......4th item down, Parts and Service, or something like that and open it up. Then look at the list of salvage yards. Call Roger in Kansas, Trenton in Sunset Texas and maybe Rob in Minnesota.  I've bought from Roger, he has many '57's and been to the Sunset Texas yard.....He has some '57's and Rob, has a few '57's as I recall.
Good luck!

Were you looking for the trim piece or the fastener?