Try http://www.bellandcarlson.com/ My .375 is on the Interarms Mark X (originally a .300 H&H) and is has one of their stocks on it. No synthetic is a perfect fit. I always have mine glass bedded. My advice for what it is worth would be to stay awat from the Ramline. Have one on my .243 and I am not really pleased with the fit.
-------------------- There comes a time when one must take a position that is neither safe, nor polite, nor popular -- but one must ask, "Is it right?"