Hi, you can get Oxbow Critical Care from your vet or on line, I have just got some for mine, and the vet recommended the herbivore type. It was really expensive buying it from the vet and when I looked i could of got it a lot cheaper online
It has everything your beardies needs, calcium, d3 etc. You can also buy Vetark Critical Care, but this doesn't have as much nourishment as the Oxbow. I add a little Reptoboost to the Critical Care which has probiotics and electrolytes, which help balance their systems and aids their appetite. Good luck