I have a friend in Moorea who sells loose pearls - PM me, if you would like her phone number. She speaks very good English.
For a Real experience in Rangiroa, at Gaugin's Pearls, for $80 you can go in a boat to the pearl-beds and snorkel to see the pearls being grown. You can also pick a string, pick an oyster and take home the pearl from it. It's brilliant! A bit like a Lucky Dip.
The pearl I got from MY oyster is an 11.6mm silver Baroque. They drilled it for me on the spot and for the rest of m holiday, I had it on a bit of fishing-twine around my neck!
Rangiroa is a Gorgeous place!