Check this site
https://www.ametric.com/section/3052/stainless-steel-balls. I bought ball bearings from here for a FJ60 steering box rebuild.
Do you recall what size balls you ordered? I reckon they're the same between the 60 and 80, although that site didn't have plus size balls.
Somehow my steering magically got better with the readjustment, even though I set it back to my witness marks from when I started. (+ or - a degree or so). the completely dead slop is now about 1.5" (in spec) but the suggestibility is very weak for another 2 inches to either side.
I'm going to put a UHMW bushing on the firewall so the steering shaft is fully supported (because 3 flex joints in a shaft = slop). The rag joint + ujoint on the inside will allow the in-cab end of the long shaft to still move up and down with maybe an inch of travel on rough roads/flex situations, just without the slop, and I think this will firm up the suggestiveness a lot.
I'm still interested in resealing with the gates kit (it does have well over 300k miles) and larger balls though since I have my parent's vehicle as an extra car right now.
I found this site from one of the CNC machine forums, in the ~0.1" size ball range for diy CNC mill ballscrews they're .24 cents each. And its made in America

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But you do have to "custom order" them though, even if it's one they end up having in stock. They don't just have a catalog with prices and all.
I reckon they'll still be under 50 cents each for our larger size. I do have a micrometer that can accurately read to .0001" (yes, tenths) for ordering them as well.
One technique to add preload on the CNC mill ballscrews is to alternate ball sizes. If you had all oversize preloaded balls, if one ball touches the next one (especially while under load) they will grind on each other resulting in a binding, rough feeling and extremely rapid wear.
But if you have a smaller ball (like one of the original toyota balls) floating between them, then the smaller ball will just rotate and since it's held nicely aligned by the track, it won't even put significant pressure on the track races (which it is now sliding against, but again it's lubricated and has very little force behind it)
Basically, if it has rolling elements it can be preloaded. The only thing that can't be preloaded is the sector shaft.