What is the cheapest site from which to buy a diamond on the internet?
I realize this is subjective (the diamonds are of different cuts,
color, clarity et al) but I am looking for something besides
Ashford.com, Abazias.com, BlueNile.com etc, maybe a wholesaler who
will sell direct to consumer or someone from Belgium or Israel selling
direct. All diamonds must be certified and the company be legit.

Try https://www.jewelryexchange.com/

Have you tried jewelrytelevision.com
Tey sell gems, jewelry, mounts, supplies, etc...