I use NSI too, I like to use Elation tips. I blend them in, then custom make a powder (my favourite so far is 3 parts Radiant Pink to 1 part Purely Pink Masque. Sorry I can't help with a natural powder though!
Do a search on here, Geeg has a 'secret recipe' for a natural powder. If I can find it, I'll pop the link down for you.