I have built the circuit in figure 1 of the datasheet and it does work, in that I get a signal across the speaker more or less the signal I have put in from the signal generator. The waveform looks a bit ugly tho, rather than a sine wave it is more square.
Oddly the variable resistor doesn't change the volume, that is up high no matter what. If I connect the earth of the variable resistor to the earth rail I get no signal. Also if I connect the negative lead of the signal generator to earth rail the signal also disappears. So i don't have amplification at all at the moment. The variable resistor may be faulty, I did have a few sparks off it!
I would like to buy the equipment to machine pzt myself but it wouldn't be practical. So I will buy it in, this means using an industrial company, there is usually a minimum order value of around £300 ($400), for that you'll get around 100 pieces. Same again with the metal you'll be mounting the pzt on, although it'll be cheaper. Glue the two together with a conducting epoxy resin. Test what you have and damp down the frequency with weights if necessary, based upon those experiments reorder pzt/mounting plates. Re-iterate until you have what you want. Rapid prototype the seal/gasket and any other parts. I'll have to buy in bulk and accept the waste. This takes months of spare time and a fair bit of cash. So yes building the transducer is more of a project than the circuitry, but one won't work without the other.