Take it to a heavy truck spring repair shop,
Mine had two broken leaves and they made two new ones and had me out the door in less than 30 min. cost was less than 100.00
In general, leaves can be interchanged but there is a varity of leaf counts and length dimensions. Can always be cut down if need be.
At least I have found it to be so between 2T and "U" model D4's.