I am accountant. And I type "000" much more times everyday. Now I am using keypad as picture below:
(https://farm8.staticflickr.com/7561/15998382147_817ba9aa31_s.jpg)
(https://flic.kr/p/qnHTCX)Numberic keypad (https://flic.kr/p/qnHTCX) by quochung19890409 (https://www.flickr.com/people/128445363@N07/), on Flickr
But I love mechanical keyboards, so I wanna buy mechanical keypad which have that function.
If it had an Fn key that your thumb rests on, and Fn-0 did 000, would that work for you you?
Something like this...
(http://www.newertech.com/imgs/products/accessories_upgrades/keypad/keypad_us_black_gall1.jpg)