I have just been having a email chat with Wayne from British Finescale who do a growing range of point work. I asked him if he had considered doing some of his 4mm standard gauge points in 21mm using the rail components from his growing EM/P4 range, he hadn't but he might consider it in the future if enough people asked.
In the meantime he is making the rail components for his A6 and B7 points available from his website
https://www.britishfinescale.com/product-p/milled-switchblades.htm
https://www.britishfinescale.com/category-s/1517.htm
So with the aid of templot 21mm point kits are now available.
Marc