look for Black Box part numbers:
ME800A-PLUS-R2
ME800A-R3
ME755A
ME890A
ME6100A
ME6101A
ME6102A
ME795A
ME796A
ME1791A
ME1794A
ME1721A
ME1821A
ME1862A
ME1863A
ME790A
ME792A
ME794A
ME775A
ME776A
ME777A
ME3000A
ME3001A
ME3002A
ME3003A

These are all point-point async rs232<->copper short haul modems. there are also multidrop, wireless, and fiber versions..