Few natural sources
Fatty fishes (tuna, mackerel, catfish, salmon) are one source.
Eggs have some; beef liver has a little. Cod liver oil has a lot. Many dairy products and some cereals are fortified with vitamin d
, meaning that vitamin d has been added to them. Of course you can also take a vitamin d supplement or multi-vitamin. Sunlight causes your skin to produce vitamin d, so some call it the sunshine vitamin.