Here is another grip for the Olympus OMD E-M5, this makes a total of 4 grips available including the Olympus Grip.
This is a Modular Grip, That is, you buy the parts you need. It has a base Plate as the starting point (part BOEM5), then it has a Grip (BOEM5-G) for the basic Grip/Plate combo. It also has a L-Plate (BOEM5-L) for mounting in a portrait mode on a Tripod.
From the Maker via a followers question about access to the USB Port with the “L Bracket” in place:
In landscape orientation you’ll have full access to that USB Port. When mounted in portrait, or vertical orientation, you wouldn’t be able to center the camera in your clamp (which is completely safe if you’re using a RRS clamp and it will have a no slip rating of roughly 50 lbs). Hanging the camera off the side of the clamp is completely fine.
However if you do wish to center the camera in the clamp while mounted in vertical orientation I would recommend the CRS Cable Relief Spacer: