You can find vt320 terminfo in the ncurses-term package on Debian and Ubuntu, however I found that most ncurses based applications (irssi, mutt, etc.) still don't behave correctly with it.
The simplest solution I've come up with is to set the TERM environment variable to "ansi" instead of "vt320". i.e. run "export TERM=ansi" after logging in.