code card

I recently purchased a 2004 Maserati Spyder. The car did not come with a CODE card. Does anyone know any easy way to obtain the 5 digit code card?

Hi Had trouble getting into car, so rep;aced batteries inside the key (it was getting lazy anyway). Same fault - discovered main car battery flat. removed, fully charged and re-fitted. Now can access the car, but won't start and the "code symbol" is lit. Seems I need to run the emergency start...