I am looking for suppliers of raw materials in small quantities for
nutritional supplement use. I mean quantities of 500g - 2 k.g. per
item.

A couple of the companies that do this are:

shfnatural
Raw Deal

I need others, as I am looking for products not on their lists such as:-

Melatonin
Non-Flush Niacin
L-Methionine

etc
 
Please provide at least 3 companies, with contact details, who
specifically deal with small quantities