best thing i could come up with: find out the extensions of the files you want to search for (10d is crw, 20d is cr2, raw is one) and search google for filetype:XXX XXX where XXX is one of the extensions. that does a search for specific extensions, but you still need a search term or google won't return any results, that's what repeating the extension is for. so an example is:
filetype:crw crw
that will give you some links to crw files