Nice collection you have there !
Like Mitch already said, the Billfold Brown p3at through cdnn is a great deal. I have had one for about 4 months now, and more than pleased with it.
The The hard chrome models, when you can find them, seem to bring a slight premium over all others. It's hard to say what a good price is for a used one, depends on what condition it's in. I have seen used models go for anywhere from 150 up to 300.
As far as the grip color, grey, green and black are standard. Navy & brown are/were a limited run.
Hope you find the right one at a good price ! Never have seen a collection of 380 pocket guns like that, that didn't already have a p3at in it ;D
Let us know what one you decide on.