ebay uk is full of them for about £40 or you could buy 20 x £2 cheapo numpads. your choice. pay to be in the club, or not.
to get full use of a mech numpad, you'd have to press each key a total of 50,000,000 times, or 13698 times each day for 10 years, or 273 times over 50 years. i just don't think anyone would press each numpad key that much