2640 Steering box

I recently picked up a 2640 for use around my acreage. The steering has excessive play so I'm putting out some feelers to learn what options I might have to tighten it up. It would be useable as-is but annoying. I've noticed that the steering wheel shaft moves up & down a bit as it is turned indicating what is probably a very worn worm gear on the end of it.

Is there a rebuild kit for these or what would you suggest to deal with this? I have searched the web just a bit and, per one comment I saw, there is no adjustment.

Dave