The Alge TdC 8001 is the Mercedes of keypad-based dedicated timers. Expensive but extremely rugged, you can drop one off a chairlift onto rock and it will survive just fine.
http://phoenix-sports.com/timer_8001.htm
Available from Phoenix Sports in Pennsylvania.
Microgate makes a unit called REI2, not as robust as the ALGE TDC and not as rugged (plastic case) but a good product and has lots of cool / compatible accessories available for it.
http://www.microgate.it/Timing...ers/Rei2/Description
I know of a used TdC 8001 available fairly cheap, if you're interested let me know and I'll fix you up with its owner.