Honestly, in this environment you might have a hard time finding that particular one. Instead and as better first choice, consider Aippi building one for you. His work is one his site and you can see exactly what he can do for you.
I think you'd be better served with a custom built 870 by home than a bone stock 870P for what is likely nearly the same price.
"Of every 100 men that go to battle 70 should not even be there, 20 are nothing but targets, 9 are true soldiers, and we are lucky to have them for they the battle make but ONE, one is a warrior, and HE will bring the others home." Hericlitus