I have given this some more thought, and maybe trying to stimulate the 5HT2C receptor is the wrong way to go, do not do this, this will worsen your symptoms. Increasing dopamine in your brain slightly decreases the serotonin output in your brain synapses as a method to rebalance your blood pressure. This decreases 5HT2C-receptor stimulation thus experiencing a decrease in HPPD symptoms. This is why levadopa alleviates the symptoms while acting on the dopamine receptors. The only downside to this is that when dopamine returns to it normal quantity, after desensitizing its receptors, your symptoms will become worse. By personal postulate; this means you have to take levadopa for the rest of your life if you're going to use it.
Maybe a way to decrease visual snow would be to kill the 5HT-receptors causing this, which could mean taking MDMA or other empathogens, pure MDMA only though; that is, not Ecstasy (Ecstasy is a cocktail drug, usually containing amphetamines or other compounds as well), since too much serotonin and dopamine in your synapses at the same time makes the serotonergic enzymes that break down serotonin, accidentally break down dopamine as well, this produces hydrogenperoxide, and that is something you do not want in your brain, it is highly corrosive due to its oxidative effects. But do not try this, this is a mere hypothesis.
Please correct any factual statements as these are mere postulates.