Lamp Part Unidentified

My wife purchased a lamp at a yard sale and it needs a replacement part I have been unable to identify. I have sent a photo to many websites that sell lamp parts, but they have been unable to help. I sure hope someone can help me out. The part is in the lower section inside the glass that helps to create a glow soft light. It hides the bulb. The top of it is missing which reflects the lamp brightly toward the top. Does any one know what the name of this internal type shade is called and if so, where I may be able to purchase a replacement. Thank you very much!