According to the Valve wiki, the status command also reveals IPs. But due to the fact that L4D/2's server search is totally broken for me, I'm unable to check. But status on a listen server does have a listing that says "loopback", which may be IP.
Yeah, I was able to check this last night while playing. If there is a client-side command to check IP, I don't know what it is. Honestly, though, I would think there might not be due to privacy concerns.
Though, if you don't have admin (modding community has their own way of getting IPs), I'm not sure why you need IPs. I assume you have your reasons though.
If you do have admin, a simple "rcon status" should work if you're logged in.
wtf stalker...
If you're that bent on tracking this player down, check the server(s) he normally plays and and see if they use PsychoStats or something like that. If they do, you can find the player by Steam ID, and see the IP addresses he's played from.
