You can actually buy this on amazon! But I like NewMind.com, same owners of Liftmode (famous for their phenibut).
I've stopped using suboxone the last week and instead substituted using this, however, I have heard horror stories of WD's from this powder too - especially since half a capsule is about 250 mg and around the world this drug is sold for use as 12.5 mg 3x a day.
It is a low affinity, full agonist at mu receptor, so you definitely feel a opiate like mood boost, nothing crazy strong, but if you are taking enough to stave off WD's from a strong opioid dependence, you'd need to use like 200 mg which is way too much and can cause WD of its own. Especially since opioid affinity is just one of its properties - it is an anti-depressent, an SSRE, and does stuff with glutamate and other brain mechanisms related to neuroplasticity that is too complicated to explain.
May be a good tool in the tool box, but be careful and don't use this recreationally on a regular basis!