Which piezo is best to replace Roland PD-120?

[glenn.szymanski]

So, I've had these Roland PD-120 pads for a few years and never gotten them to work with Megadrum. I had a tech wire some resistors into them, but the positional sensing still won't work because of the positive or negative half wave (I forget which). I'm thinking about just replacing the piezos in the 3 pads that I have to avoid all these problems.

Has anyone done this? If so, what is the best piezo to use?