The Linking Finger Ring Project by David Regal is truly a gem.
It’s not cheap but neither it is so expensive you would rather salivate than buy it.
If the price is a concern, though, you can buy the lower-end Himber type rings. I have one I bought many years ago for around $30. It may be in the $50 range now.
While it works, the old Himber ring is super difficult to perform smoothly. There’s a lot of fiddling involved when linking and unlinking the rings.
I have been waiting for the linking ring that eliminates the fiddling, and I found it when David Regal put his set in the market a few years ago.
Its price is mid-range. There are more expensive sets in the market, but Regal’s works like a charm at lower the price than most professional-grade himber rings. The routine that comes with the set is beautiful. The handling eliminates much of the fiddling.
I need not go up the price ladder anymore to perform a beautiful linking finger ring trick.