I've been making IMAM with ascorbic acid from: http://www.naturesbest.co.uk/
and it does not have the yucky taste of the IMAM made with C from purebulk.com.
I tried the British stuff because I read that they are not allowed to use Genetically-Modified-Organisms to make ascorbic acid. Shipping is reasonable to Canada.
purebulk told me that their ascorbic acid is made from (gack! I forget the name!).
That something is made from corn, and the manufacturer may claim that it is non-gmo corn.