Excellent keyboards made by
IBM to resemble selectic typewriter keyboards. The "clicky" sound was caused by a buckling spring. The IBM keyboard technology was eventually bought by
Unicomp, who still makes the clicky keyboards. The web store http address is
http://store.yahoo.com/pckeyboards/ibmkeyboards.html
IBM made a clicky keyboard without a
numeric keypad to save desk real estate. It has part number 1391472. Don't buy the short keyboard at the url above, it's got weird key placements at the lower left. I think you can find the short keyboard at
http://www.pckeyboard.com/ibmlist.html
But these things show up periodically on
ebay
too. Try there first, as you may get one for $5. The last one I bought cost more for the shipping. If you are concerned about wear, don't be -- they're practically indestructible.
Another product that was influenced by the IBM M series keyboards is the
Linux Cool Keyboard. Not as heavy, but reportedly a similar feel.