Not the wine making grade, but the commercial grade.
The kind that can be used to replace oak bark.

Like everything else here I know one of the members has the name of a source!

Oh come on with the varied background of the folks here and everybody is as uninformed as am I of a source???

Don' t know if this is what you are looking for but it took less than 2 minutes Google it.

https://www.parchem.com/chemical-supplier-distributor/Tannic-Acid-Industrial-Grade--021587.aspx

Interesting, I keep getting wine maker grade in my searches.