There are currently NO ONLINE LOBBIES for MW2, they were all patched with the last TU update. However there are various trusted people that can still do this for you through system link, I don't think I'm allowed to post links on here however feel free to PM me.
Currently however, as only a few select people have the knowledge to do this, your looking at $30 for 10th in MW2 with everything unlocked etc.
Regards.