Broken pneumatic distribution block
I do not own such piece, so cannot tell if they all are broken by this time. However I have a suggestion regarding acquiring a replacement.
Bricklink is a dedicated to trading just LEGO items, so I can recommend to look here for replacement. While some of the sellers do not check functionality of all the items they sell it is considered items should be in a working state unless stated otherwise. It would be best to ask a seller (that you have chosen to buy the item from if it works) to test the piece if you ask them before placing an order.
The item you should be looking for on Bricklink is called Pneumatic Distribution Block 2 x 4 with Non-return Valve.