You mean the big metal jobs with the "clicky" feel? I still have a few and use them daily. Do a Google search for something like "IBM clicky keyboard" and you'll find lots of them available.
I have one or two that were made for Dell and came with some Dell desktops we bought 10 or more years ago. I was pleasantly surprised to see that people are willing to pay extra for these, e.g.
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... gory=33964 I really should clean out my basement. There's gold in them thar piles of "stuff."
(IBM actually used to make their own keyboards. Remember they made Selectric typewriters and 327x computer terminals for many years, not to mention the keyboards for their early PCs, until they sold their keyboard manufacturing facility to Lexmark. The newest "clicky" keyboard I have was made by IBM Mexico in 1993.)