I think this should do what you want.
The components to the left of C1 make up a DC supply whose voltage can be set from ~7V to 50V. Components to the right of C1 form a full H-bridge for square-wave driving the piezo in response to a 0-5V square-wave input from a function generator. The advantage of using an H-bridge is that piezo displacement amplitude is twice what it would be for a single-ended drive arrangement; thus the amplitude swing can be up to 100V while the actual voltage across the piezo is up to 50V (i.e. within the 54V limit mentioned above).