Hey,

What are some natural sources for cyanocobalamin?

Cyanocobalamin is not a natural substance. It is man made.
It may be added to some cereals. It may appear on some ingredient lists.

Cobalamins without the cyanide appear in animal source foods.
Meat, seafood, eggs, milk. They are combined with protein, and must be "freed" during the time in an acidic stomach. Then intrinisic factor carries the cobalamin thru the intestinal wall.
No acid=no absorption
no intrinsic factor = no absorption

Natural cobalamins are present in food in minute amounts...and need this assistance. When taken orally as a supplement, much higher amounts are needed so that they can pass into the blood without intrinsic factor. This is called passive absorption.