I hate to be one of those "use the search function" people but, seriously, any search in this forum for "PSP", "P7M8", "P7M13", etc. will turn up a lot of info (most of the threads will be common between these guns).
My post in the following thread should be of some help:
http://canadiangunnutz.com/forum/showthread.php?t=776144
These things always seem to go in cycles. Right now P7's are very scarce. At various times in the past, including a year or two ago, that was not always the case. The demand and the prices will continue to rise, and that (among other factors) will cause there to be more P7's showing up in the EE in the future. Right now I don't think there are any, but there were a few a couple weeks ago.
When Armtac brought in PSP's, and then P7M13's, some of the guys I hang around with at my range thought that Chris might depress the prices a bit. That hasn't happened. If anything he
created more demand, and way more demand for things like P7M13/P7M10 mags!
Chris, find some more in Europe and bring them in! Like K98k's the demand never goes down for P7's.