CaMg supplement without Nitrogen?

I've been using CalMag by Botanicare for some time but have found that it seems to provide too much Nitrogen leading to N toxicity within veg and flower when used alongside Pure Blend Pro Grow/Bloom at 5ml per gallon, which antagonizes Mg, K, and Cu uptake. Symptoms include purple stems (Mg), yellowing of lower leaves (Mg) with rust spots (K), and some yellowed edges of newer growth (possibly Cu) in addition to the obvious clawing and twisting of a Nitrogen overdose.

I'm wondering if anyone has any recommendations for a standalone Ca supplement or a CalMag supplement with a 5-1 or 3-1 Ca:Mg ratio that DOES NOT contain any additional Nitrogen. I know Fulvex is a great Mg supplement but have had a hard time finding a water soluble source of Ca to add with it. The only standalone Ca supplement I have found is Calpex, and I'm wondering if there's anymore out there as Calpex seems difficult to find.

Dolomitic limestone has both calcium and magnesium in the carbonate form. It doesn't work
as fast as Cal/Mag so it's best to use it mixed into your grow medium when you start growing.

Epsom salts has magnesium sulfate and gypsum has calcium sulfate.

Dolomitic limestone, epsom salts or gypsum don't have nitrogen in them.

Grow More makes Mendocino Flowering Cal-Mag.
No nitrates. 2 to 1 ratio, but I have had good results with it.

If you are using beneficials, Demeter's Destiny (Nectar from the Gods) is perfect with Pure Blend Pro.
It supplies the calcium and pulls the magnesium from the coco.
Highly recommended.