I am having a similar issue.
I broke my PING))) sensor, and have removed the transducers from the circuit in hopes of being able to use them again.
I have been searching online for a circuit to drive them, but have had little luck.
I have found some circuit diagrams, but I am having some issues with figuring out how to use this with an arduino. They seem to be stand alone circuits, and I want to control them with the arduino code.
here is a link to some of the info I have found. If you or anyone else can make heads or tails of it, and suggest how to use this with the arduino, it would be greatly appreciated.
http://www.next.gr/audio/ultrasonic-circuits/ultrasonic-transceiver-l13839.html
http://www.next.gr/other-circuits/switch-circuits/Ultrasonic-switch-circuit-l7910.html
http://www.next.gr/audio/ultrasonic-circuits/ranging-system-l13831.html
those links seem to be the most useful I have found, but I am still too new to electronics to figure out exactly what they are doing, and I would prefer not to burn any more components trying to figure it out on my own.
Hope some of that helps, and if you figure out how to use this info, please share
N8
ETA: it seems to me, you might (or should) be able to use the Arduino in place of the 555 timer on the transmitter to send out the ultrasound pulse, then use the dual op-amp circuit for the receiver. I do sort of understand how these circuits are working, but not well enough to integrate it into the arduino. At the very least I am thinking you could trigger the 555 with the arduino, but that seems redundant to me, as the 555 can handle the triggering all by itself. I am mostly at a loss on how to wire this to an arduino and how to handle coding for it.
This is also assuming that the transmitters and receivers are all the same or similar, which is doubtful, or there wouldn't be so many different models of them.