Looks like the Taurus boot grips are still available:
https://www.shoptaurus.com/revolver-...r-grip-5-20880
Not that I took it all the way through to an order...
I've tried multiple grips on my j frames and the Taurus are simply the best plus very cheap. They do have a metal plate. To install you'd need to either remove the grip pin from your J or else drill an appropriate hole in the grips.
All that said, I still sometimes get cut / rubbed by the cylinder release with full power loads in an air weight with a thumbs forward grip. I usually go for a thumbs wrap grip on the j accordingly. Of course depending what else you shoot could lead to bad habits.