Have you looked over at Rock Auto?
They have the LARES reman units.
If the worm and sector are still good in your box then ChevsOfThe40s
has the rebuild kit for a DIY project.
I have zero experience with either. On my '49 fastback the steering box adjustments from the manual were all that were necessary. All of the freeplay was a result of wear in the third arm pivot pin/shaft (causing the third-arm to deflect up or down during initial steering inputs). Between the pivot pin and the tie-rod ends it is now good as new.
What symptoms you are trying to cure?