Instead of creating new July 4th items for Independence Day, Happy Pets is rereleasing some old Limited Edition items, namely, Captain Kitty, a star-spangled Uncle Sam Hat, and a USA Flag with a stand attached.
All three items were previously released for Memorial Day, so this is ridiculously lazy on the part of the game creators. Then again, maybe they're counting on everyone being too busy vacationing during the ID4 weekend to care. On the upside, the three items are being sold in a bundle for 60 Facebook Credits ($6 USD), instead of 98 FB Credits ($9.80 USD), so you'll be saving in you grab 'em this time around. The Kitty itself was originally 88 FB Credits ($8.80 USD).
This offer also isn't available inside the in-game store. To find it, you'll need to click on the little "4th of July Sale" icon on the left side of the game screen.