DAGS. There are plenty using the key words "Glass door knob lock".

Gotta buy three to get these:

http://www.buyhardwaresupplies.com/?...emNumber=50360


then there are these guys

http://www.lookintheattic.com/door-k...FSAgDQodTn0DSA

There are plenty more, including more folks selling retro kits.

For me, I would buy the whole lock somewhere. Kwikset quality is
middling to poor quality, and if the locks are that old and are in
constant use, I wouldn't give replacement a second thought if I was
going to be hanging around.

Robert