Skuzzy had mentioned a while back when I was talking about the differences between modern gaming mechanicals and the Old IBM Clickys that you used one in the office. I found a bunch at a small PC store, and have ample back ups as well now.
There is only one place that makes the same buckling spring key that feels the same as the old IBM M's. Here -
http://www.pckeyboard.com/.
These guys do a pretty good job if anyone is looking and can't find a good used one on Ebay. There is nothing like typing or gaming on them IMO, I've tried Razer's, Corsair's (several different types of cherry mechanical keys), and Logitech's at various stores and such. Nothing touches the old buckling spring of the IBM. Many of the 1994 to 1997 IBM M keyboards were manufactured by Lexmark under contract, but there is no difference between their feeling that I've ever been able to tell, and wouldn't even have known without reading about them at
http://www.clickykeyboards.com/ . Some used ones for a decent $ can sometimes be found here, Ebay has quite a few right now as well, good time to strike.