Rebuild kits for both the John Deere/Bonney and Thorsens are NLA. Best option would be to keep an eye out for another ratchet of that type that's externally buggared but has good innards. Then do a parts swap.
If I had things to do over again, I'd snag every used ratchet I could and sort them out according to what I've discovered in the ratchet thread. Then, when I or someone needed a rebuild kit, I'd have those parts available. Hindsight is 20/20, you know.