They actually have. It's called the Pro Growers mix and it uses Coco instead of Peat. No fertz and PH balanced.
The website has more info http://www.northcountybounty.com/
The Silica in Diatomaceous Earth isn't what kills the Fungas Gnats, it's the fact that the Diatom skeleton's are very sharp so essentially the Fungas Gnat's Larva is getting ripped to shreds as it moves through the soil.
If you're using rock dust minerals like Azomite you're getting all of the...