Honestly, if it is a reliable US source, then it isn't attainable thru illegal pathways unless someone at a pharmaceutical company or pharmacy is willing to skim from the company...
Most "US" sources are getting their raws from China for just about any prescription only or controlled substance. Reliable sources are going to have to be overseas and particularly I'd consider only a handful of online pharmacies. Most are coming out of India.
Also, if you have a good AI, some T3 and perhaps some mucuna pruriens, you will not need the Prami while running the Tren.