I use one by Winthrop Holsters. Scroll down until you see the one for the XD and then imagine it even smaller.
IWB for XDs
It is a good value for the price and seats the pistol as low as you can get, which minimizes printing onto the outside of the untucked shirt. My only complaint is they didn't use the more expensive Lift-the-Dot snaps and hence it may take several tries to get the snaps fastened so they stay snapped.
Bart Noir