Tribe,
Update for this project:
I ordered the part needed to proceed, the "tow hitch ratchet cog repair kit" from the only supplier I can seem to find, which is powerfuluk:
https://www.powerfuluk.com/products...pGqJoqWeYpQBNBfRlZuMfvabALB59IhGT9KCwiIdZxHLN
Unfortunately, this is yet another part powerfuluk refused to sell to me purchase because it appears they don't like me, and in any case won't sell to me (I tried this time direct sales through eBay rather than their website, which they insisted I use the last time, but they this time again denied my purchase and after taking my money, refunded the charges in full; screenshot attached).
So yet another terrible customer experience and I simply cannot recommend https://www.powerfuluk.com/ to anyone and am even a bit ashamed I had to go to them in the first place (after my last run-in with them). Perhaps they simply hate Americans or sending things to America.... Or just me.
Funny how business works, or doesn't.
Since www.powerfuluk.com is the only supplier I know of who make this part, my OEM trailer hitch rebuild project is now officially over (unless someone has this part or knows of where I could get it).
And as @powershift recommends - I will soon be in the market for an improved aftermarket hitch receiver - suggestions most welcome!
So on the other hand...perhaps I should instead thank www.powerfuluk.com for being so unhelpful so I could ditch some stuff which I could get better elsewhere in the end!
I provided a link above; in the video they mentioned where they found that part:

Perhaps give this a go?