Suggestions on a front or a one piece rest for a six inch wide forearm rifle

[Alan Witter]

I just acquired my first heavy rifle. Where might I start looking for a front rest for a six inch wide forearm with runners (for lack of a better idea to call them) that are at each side of a plate under the forearm and protrude below the plate maybe a quarter of an inch.
I will consider a front rest with a rear bag, or a one piece rest.
Thanks very much for any suggestions.