Oily fish is an excellent source and lists of food can be found by Googling.
I'm not surprised Amway supplement is expensive, but a year's supply of Healthy Origins 5000 iu D3 costs £13. I have been taking this for years and used to have to import it from the USA. I now get it from Ebay uk, but you will probably be able to get it your side:
Content on HealthUnlocked does not replace the relationship between you and doctors or other healthcare professionals nor the advice you receive from them.
Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked.