I just purchased ALL EIGHT of my Colorbox Petal Point reinkers from one site. Try: blockheadstamps.com.
I don't know why so few places have reinkers. My Colorbox Petal Point is Chalk Primary Pastels. To find all eight in one place was a find.
They also have very cool stamps their own designs and carry Lost Coast Stamps designs if you like steampunk different sort of stuff. But I only ran across that because of the reinkers.