Read at least one of his books, all good advice does not come from doctors alone.
Read a little further, vitaspace has been in business for 22 years so you are probably correct about the web site. They have a grocery store as well as selling bulk nutritionals to the packagers that the public buys from. Peter will sell to individuals if he believes that you will be careful with measuring.
Want D3? He has it, 500 grams for $80 - 100.000 IU per gram. That's enough for a few years.