When I mine had mites I used most of the methods on everal different scorps as they were in a communal tank. They were also about the same size as yours because they were 4th instar emperors.
After a little while I managed to get rid of them all through submerging, vaseline on cottonbuds etc. For the last two scorps I had to resort to breeding my own predatory mites.
I had to try this on three occasions before I got some. I had a tiny tiny glass vivarium of which did not have any scorpions in. I left two dead crickets in there purposefully so that they wopuld decay and attract mites.
Every time mold began to grow, but on the third attempt, I had several of the predatory mites covering the cricket carcases. They are orange-reddish in colour, tear drop shaped, and are much larger than the "bad" mites and will move around.
I gathered as many as I could off the crickets and put them into the polystyrene deli cup that the scorp was moved into to separate it from the rest until it was clean again. The next day, the predatory mites were on the scorpion running around, but I could see them clearly devouring the "bad" mites.
Another day passed and only a couple "bad" mites could be seen.
Eventually, only predatory mites were left which then disappeared and supposedly died (as a result of having nothing to feed on) which then left me with a very clean now happy scorp, that could be re-introduced to its siblings in the communal tank.
I used this technique successfully on two 4 instar emperors, however, it took 3 or four goes at getting the mites before I actually got them. Also each time, I left the crickets in there for two to three days, checking daily.
The majority of the time, there was only mold, but the times when I had the mites, there wasn't as much mold but would have plenty of mites.
So perhaps, you could give that a go - It worked for me!
Why buy some, when you can breed your own for free.
