John Britts book Mid Range glazes has plenty of recipes along with Glazy. The issue with crystalline glazes is that you need to control the temps and they are extremely runny. This coming year I'll be making a small test kiln controlled with a digital controller to experiment with.
I was dragged into the world of crystals because people like them, but it's not something I was attracted to naturally. There are many mechanisms of crystalline glazes, and some are better for bonsai than others imo.
The super large zinc/frit crystals are a recent western invention and I personally find them too loud for bonsai. I recommend Fara Shimbo's book if you want to make these.
Then there are the subtle crystals from Japanese potters like Koyo, Juko, Tofukuji, or Ino Shukuho. Completely different mechanism and less runny, but these glazes are natural formulations. There is more uniqueness to these glazes and each pottery's glaze is their signature. As you can tell this is the route I prefer and I am working on my own signature glaze.
I will say that my crystal game improved a lot when I got a huge kiln, because the thermal mass cools much slower. So play with the hold temps
