The M203 Grip is a good idea -- once you start using a vertical grip, you come to miss it when it's not there -- but it's way overprices (almost $250:
http://www.ustacticalsupply.com/inde...S&Category=117 )
All things considered, I'm surprised no one's come out with a replacement M203 handguard with it's own accessory rail (two half shells with a recessed rail inside a wider channel; mount the grip of your choice, or use a regular RIS cover plate to return the grip to its usual rounded configuration with nothing sticking out.)