Ideally a lockout system will lock out ALL other players upon the first buzz-in. There would then be a separate reset button operated by the emcee or judge which resets the players' lockouts.
You also need an indicator to show which player buzzed in. If you could map your lockout buttons to, say, numeric keys, all of this would be easy to do with a simple program which could also play a sound effect.
For a more economical solution, do a google search on "pendant switch".