pointers:
-never buy powder, always whole bits of root then grind yourself.
-sow your seeds anyway, whilst still looking for root sources.
-contact https://theherbalist.worldsecuresystems.com/index , he grows his own, but may be reluctant to part with any non tinctured root.
-if all else fails, why not whole root peices from India? Its the home of Ashwagandha after all.