Quietly slipped in with the "Save Carmine/Carmine Must Die" shirts for Gears of War 3 is this Child's Play shirt.  If you don't care either way for Carmine's fate or Gears of War 3, but sill want to do something for charity you can buy this shirt for your avatar.

For a measly 80 Microsoft points you can get the Child's Play shirt for your avatar.  You have to act quick though, it's only available until September 1st.  As the description states;

"Support Penny Arcade's charity Child's Play by proudly wearing this tee. Child's Play donates games, toys, books, and cash for sick kids in children’s hospitals worldwide. Get your shirt in time for PAX West! The tee is available only through September 1. A portion of the proceeds from this item will go to Child's Play."

Direct link to Xbox Live to purchase the Child's Play shirt.

Below is an idea of how it looks on your avatar.