Awhile back, I wondered if you could use a 3DS XL case or grip on an XD, since it was a duplicate design. Trick was, the GPD is just a tad smaller.http://boards.dingoonity.org/gpd-devices/3ds-xl-accessories-for-gpd-xd/msg127748/#msg127748
Well, after getting tired of hand cramps after very short playing times (not GPD's fault, it's the darn XL design that they copied), short of trying to stick the XD guts in a G5 case - A total impossibility - I decided to order up some "grips" to see If i could adapt them to work with the XD.
The answer is - YES! The dreamGear comfort grip (us amazon link: http://www.amazon.com/dreamGEAR-Comfort-GRIP-Protection-your-Nintendo/dp/B00UJ9LB6Y
) can be "adjusted" to work with the XD!
The trick is to create a U-shaped insert for the bottom and sides of the grip, so the Xd fits in snugly - it's a tad smaller in both width and depth. You also have to trim away the back lip on the grip that normally fits over the back of the bottom half of the XL - the non-screen half of the XD is actually a tad thicker than the XL, so instead of laying flat, it sticks out due to the ridge. The Back buttons are basically in the exact same place as the XL, so once you remove the lip, it rests against them and they work with no problem.
It's not perfectly pretty - but it's AMAZING to use - Totally comfortable and cramp-free - And I can still pull the silicone grip off for travel, if I don't want the bulk. I can still access all the back slots (you have to move the back around a bit to plug things in) and none of the top-face android or controller buttons are covered. The speakers are MOSTLY covered, but there is one hole open on each side, allowing good volume without having to punch any holes in the silicone.
The hinge-space on the XD (between the bottom and top halves) seems to be tighter than the space on the XL - that plus the thicker bottom half makes getting the bottom half of the grip over the hinge a bit annoying, and it sticks up a bit - that's the not-so-pretty part - I suppose you could cut that hinge-portion off on both sides, but that lessons the solidity of the back. I chose to snip the sides of the top half that slides under the hinge - this means it simply slides on and off - but it's not really going anywhere. Actually, you don't even have to use the top half, if you don't want to - I have it on because this now doesn't fit in my normal 3DS Xl case - it IS a case, basically.
Here's some pics: