tonysforendsandgrips.net That guy can make anything, and it looks great!!! Will custom size to your hand as well.
I've got one of his forends on my 460.
This picture doesn't show it very well, but the forend is vented along the top edge. He can do them without the vents, or whatever ya like. He does have a recoil reducer grip also. Got one of those coming after the first of the year to match this forend.
And no, the grip won't be vented!