Sources: Fish (generally fatty: trout, salmon, tuna, herring, sardines, tilapia, flounder), Mushrooms (some, large variety in quantity).
Note the article is "food sources" so it includes fortified (dairy, juice) which do not contain vitamin D naturally.
The substance in mushrooms (ergocalciferol) has a structure similar to the true vitamin D (cholecalciferol a.k.a. vitamin D3).
Nevertheless, it seems that it is not able to substitute vitamin D in all its functions. Therefore it is not advisable to count on it as a source of vitamin D.
There has been a company that has claimed that they have discovered a species of lichen that contains true vitamin D. Nevertheless, their advertising has seemed highly suspicious and it looked more like a scheme to separate naive vegans from their money.
Even if it were true, exploiting wild lichen would be much more unethical than eating the normal vitamin D3 supplements made from sheep wool. The reason is that wild lichens grow very slowly and exploiting a species for a food supplement would cause a very high risk of extinction for that species.
In any vertebrate animal, the liver is the part with the greatest content of vitamin D.
Uh. Okay buddy, thanks for that.
P.S. most milk sold in the US is Vitamin D fortified.