I get mine at Petsmart http://www.petsmart.comor Petco http://www.petco.com. Mine are in driving distance. I believe http://www.joshsfrogs.com also carries calcium supplements. You can even order some supplements on ebay, but I would stick to commonly used brands.

They need more calcium and vitamin D3 than in the mvi alone. They often exhibit signs of tetany before MBD. Signs of low calcium can include twitching, uncoordinated movements, tremors, seizures, paralysis. If your little fella is in the beginning stages of MBD, you can stop the cascade by providing the calcium/vita D3 and mvi supplements.