Given the off shoring of Jacobs chucks I believe you're better off buying used and rebuilding as necessary. Its fairly easy to tell if a Jacobs chuck was made in the US or China. The US versions will have Jacobs, etc engraved/roll stamped in the body. Chinese versions are laser etched.
Personally when & if a new chuck needs to be purchased I'm going with a Rohm. BTW, an Albrecht is also excellent.
Personally when & if a new chuck needs to be purchased I'm going with a Rohm. BTW, an Albrecht is also excellent.