Its sold as bonzai tree nutrients or something like that, you just have to look around.
People around here like to keep their RC vendor websites to themselves in fear of the substance being made illegal.
If you do find it, be VERY carefull.. If you dont have a milligram scale, DO NOT GUESSTIMATE! I "overdosed" my first and only time because I estimated an appropriate dose that ended up being 5x more than recommended. Terrifying halucinations, sweating bullets, vomitting ensued. I remember thinking that if I still had my motor skills, I would kill myself to end it as I was sure I was going to die anyway. I woke up 4 hours after dosing and had a new, intense appreciation for life. As far as Im concerned, it was my only near-death experience.
So be carefull, buy a mg scale, or buy some Spice.
Good luck