if you click on my name here you can send me a private message through the forums or click on the link to send me an e-mail or just use artist(at)eh21.com
The p20 backs come up about every other month on ebay, and there is one for sale there now ( but not really a great price) and probably through dealers you can locate one too. Actually you might contact Optechs Digital in Seattle, WA as they will have my P20 back that I just traded in.
You can also fit many other digital backs to the X-Act2 using sliding back adapters and inserts. The Hasselblad ixpress and CF backs are well integrated with the lens controller s and you can buy the needed cables or adapter plates directly from them.