Olympus E-PM2 battery grip or removable battery

In my latest steampunk camera box, I am putting a E-PM2 inside of an Acid Cigar box:

Olympus E-PM2, Gariz leather case inside of Drew Estates Acid cigar box

The E-PM2 does not support a battery grip.  At present, I have the camera in the Gariz leather shield which I bought for when I'm shooting hand held, but for the steampunk camera it has the nice effect that it moves the tripod socket away from the battery compartment, and it has an opening in the case for changing batteries.  So I made a base that has a hole, so that I can change batteries:

Olympus E-PM2, Gariz leather case, wooden base to allow changing memory card/battery

However, it is clunky to remove the camera from the box, or turn it upside down to change batteries.  Now on the big box with the E-5, I have the HLD-4 battery holder, which allows me to change batteries from the back, and if I didn't use that, I could potentially use the PS-LBH1 battery holder, which takes 3 CR-123A batteries, and hack the holder to use an alternative power supply.

I'm wondering if there is a 3rd party grip for the E-PM2 (probably not, after all it is the low end camera in the current line up), or if there is a holder like the PS-LBH1 that I could mod to connect to a BLS battery in a different location that is easier to change.  I imagine I could make something the same size as a BLS battery with wire contacts in the appropriate place, and attach a battery to that, but I was wondering if somebody had already do it.