This can be a problem with "no-name" disc brakes, nobody knows where to get replacement bits! If you have had no luck, try contacting the bicycle manufacturer, or it's importer to see if they have any ideas. If they (the importer) doesn't know where to get replacement pads, or who does them, and you have exhausted all other means of finding out, make a point on something along the lines of it being not very good supplying a product that has no replacement parts. It may get you somewhere, it may not, but there would be nothing to lose if you can't get a replacement pad, as then you'd be looking at a new system/caliper.
Hope that helps.
Aaron