Hub locks are dirt cheap, about ~ $75 from the dealer when I last put one on a customer's truck. All the same, can't recall if that was a vacuum lock or a manual type.
FWIW, if you are 'unable to turn' one of the hubs and you have an auto vacuum lock system then the whole works is likely toast due to debris, corrosion and dirt intrusion: hub, both inner seals, hub lock and seals, vacuum lines, 4x solenoid, 4x vacuum regulator. These systems do not take well to contamination.
If you are unable to turn one of the hubs and it is a manual shift then just slap a new lock in there and go on your merry way.
2003 GMC Sierra 3500 -- dually, 4x4, hasn't blown up yet and that's what i look for in a truck
Ford Doctor -- They come in broken and leave fixed. Ford of Canada Master Tech