Have you tried any of the Foggy's haze fluids? http://www.froggysfog.com/c=KKbbdT9YqV3Wk8HVBuoyF1SnH/category/10-fluid.20-haze/
They have different densities of haze and fog.
I have used the froggy's neutronic haze fluid made especially for the radiance and neutron hazers and have found it to be the equivalent to the ultratec's fluid, except $60/gallon cheaper! The radiance and the neutron fluids are mixtures of glycerol and water and that's it, hence why I dilute my fluids with water to lesson the haze effect.
Their oil based fluids (mineral oil) are definitely not compatible with the radiance or any other heat vaporizer type hazer/foggers. They are designed for oil based crackers (df-50, etc). As far as the other water based fluids they sell, those are water/glycol mixtures designed for traditional fog machines. Although they work similar in principle, I'm not sure that the heat exchanger design or pumping pressure/volume on the radiance is compatible with vaporizing those types of fluids. I suspect it isn't. I wouldn't even think of using them either as they smell and are hydroscopic (they adsorb moisture from the air / eyes / nasal cavities / mouth / throats of vocalists, etc) hence many people complain of being allergic to them. The price of the Radiance is well worth the comfort of getting away from gycol based fluids.