Before you run out and order custom thank you notes with your names on them, pick up a few boxes of something in the bridal spirit.
Since you may not find the perfect formal card right away, and it may take sometime for the order to be delivered, you should have a few cards on hand for engagement gifts that arrive sooner than expected.
These
Bling Bling Thank You Notes by Greenwich Letterpress may not match the exact design of your rock, but they still get the point across.
The cards are sold in sets of 8, giving you 2 cards in each design and cost $16 for a set.