You can get original nokia spare parts at nokia care(official nokia service centres) but the original spare parts are horribly expensive and its better to get a new duplicate panel for lesser price than paying for just keypad(original).Here is the link for nokia care centres:
I have bought non nokia replacement housing for my E51, but the quality is not at all good. The parts got damaged really fast. I suggest you get an original panel from Nokia Care itself eventhough it will cost more.
Lol, the buggers tell me that the original keypad membrane is around 2100 phuuuuuuuuuuuuu, this is an very old model, nokia should reduce it price at least, another reason to hate nokia.
try ebay.com in case u have a paypal a/c, i replaced N73's entire keypad module as joystick got damaged, works fine costs around $2 shipped to u doorstep via HK post.Quality is much better than indian duplicate spares.