I believe there may be a secret plot to corner the world's known supply of earbud covers. The spongy little things seem to disappear all too frequently.
Revelant History seems to try to keep up where you can buy them for the manufacturer supplied earbuds that come with Applie iPods.
; "Christmas Treats")
; "David Carr of the New York Times")
; "FLDemocracy2012.com")
; "4178265189_4785cf3fa5.jpg")
; "9-22-11-2.png")
; "markgalsergplus.jpg")
; "IMG_0520.JPG")
; "Knox County Cell Calls on AT&T")
; "Bonnaroo 2011")
; "Sourcing Stories")
Google+
FYI, I too have been looking to find replacemnet covers for the foam pads for my walkman. On the web, I found a company that sells D-10 foam earbud style covers in bulk. 500 for about $18 dollars. Check out www.scansound.com