Roughly 1½-2 years ago, I was looking for make-it-yourself sweetener options, and looked at Stevia discussions. ECF has (had?) multiple threads on the topic. As, I recall (and I may be totally wrong... please verify for your self
), the primary concern(s) were "secondary" ingredients. Anti-caking agents for the powdered/granular versions; and "stabilizer/freshness/preservative" agents in liquids (fine for ingestion/unknown for inhalation). I couldn't find anything, in my own town, I felt comfortable with; so, I personally chickened out, and bought a small bottle from an on-line DIY vendor.
To help you with your own investigation: I did a quick search on ECF, in the DIY E-liquid sub-forum, for Stevia ("search titles only"), and limited the search to only the DIY sub ("search this forum only"), and got back a manageable 39 hits.
View attachment 678505
Here are my search results, if you don't feel like doing your own:
Stevia search
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