You can charge up mushrooms with vitamin D (D2) by placing them in direct sunlight for 30 minutes. Any ordinary mushrooms. So salmon (D3) and charged mushrooms would do just as well.

If you're not vegetarian you can try cod liver oil, e.g:

https://www.norwegianpharma.com/our-products/norsk-tran

https://www.mollers.com/product/mollers-tran/

Vitamin D pills.

Look for lactose-free milk, typically color-coded in purple tones.

A2 milk