Looking for Equisetum Hyemale / Horsetail spores

I recently watched a video that suggested this for dental health.  I found a place to buy the powder but I'd ideally like to grow my own. It seems this plant is common most places, but I've never seen it here.  Because of my location (Saipan,
a US commonwealth) I can't ship in bare root plants but seeds or spores sent from the US are allowed.  Does anyone know where I could get spores from?  I've done a search and no luck yet.  Thanks!