I looked at the most recent craft video in my subscription list that uses them, but all the crafter calls them is "basic pearls."

However, Googling for "Self Adhesive Craft Pearls" brought up a lot of hits. I don't know how well they'd attach to fabric, but if the adhesive is strong enough to endure the postal service, and arrive at their destination still attached to the card, as intended, it's got to be pretty strong.