###Prior editions have precedent
Prior editions have precedent
I have not found any official non-magical item that does what you want in 5e sourcebooks. Most likely, you're going to be dependent on your DM allowing whatever you do, which is technically the case even for things explicitly stated in the rules anyway. If you or your DM doesn't want to simply allow "Fog Cloud without spending any spell slots or other resources, and which cannot be dispelled because it's not magic" then you could negotiate an alchemical tool for the job. Alchemical tools do exist in DnD 5e, such as the Alchemist's Fire listed in the PHB, but none of them explicitly produce obscuring smoke. However, precedent from 3.5e gives the smokestick that could be ported to 5e. It's the closest I know of to "non-magical potion of fog".