I had no luck finding any reliable source on where one can get Golden Razz Berries. I could imagine getting it either from raids or from pokestops (or maybe as a level-up reward).
Does someone have any reliable source or has maybe even experienced theirself where Golden Razz Berries drop?
Best Answer
You can only get Golden Razz Berries as a drop from defeating a raid boss. The higher tier the raid is, the higher number of drops you can get, including Golden Razz Berries. I've personally received 10+ from defeating tier 3-4 raids.
From Pokemon GO Hub: