Please help identify antique bulb and where to purchase

I think it's the perspective...

 

This site has a small selection of old lighting sections from catalogs 1910s through 1940s. The owner of the site has died, so the site may disappear suddenly and unexpectedly without warning at any moment. You could flip through these catalogs while you have the opportunity.
https://www.oldhouselights.com/catalogs_frame.htm
I flipped through some of the 1920s catalogs. It does look like some light fixtures came without shades. In the 1920s catalogs it shows them with round frosted bulbs.




If you go to the homepage and click on what the site owner calls the "pan" category of fixtures. Yours looks like configuration number 3.
https://www.oldhouselights.com/homepage.htm


The internet archive has thousands of old catalogs. By a stroke of luck you might be able to find your exact light fixture poring through them.

Also you might want to do internet searches for historical house salvage, urban archeology salvagers, architectural salvage, etc.
https://www.oldhouseonline.com/interiors-and-decor/where-to-shop-for-architectural-salvage/