Those typical photo printing shop do sell them. Cheap too, $3.50 one big bottle. I can't even finish using it for my camera, therefore i also use some of it for my computer hardwares stored in my cupboards.
Silica gel it self is non-toxic, but the Cobalt Chloride, which is use to make the color of silica gel can cause cancer in animal. Still there is no evident show that it can cause cancer in human, so it is still allowed to use as silica gel humidity indicator.
Just wonder is there silica gel without humidity indicator for sale, because with the build-in humidity meter, color indicator is not so necessary.