If it is a remote key fob I bought one second hand on ebay as Honda only supplied one fob and two keys when new, they wanted about £130 for a second fob when I bought it in 2006. The circuit board inside the fob has a code on it and you need one with the correct code for your vehicle, there is then a process to go through to link the fob to your car (I found it online somewhere and it worked first attempt).
I don't know if all the early cars had remote central locking fitted, my 2003 1.4 SE does, I also don't know how you would find out what your code is without another fob to get the code off to start with. Think I paid about £20 for mine.
Mine is a two button fob, don't know if the 3 button to be would work or not.