x920d is the Taiwanese International variant of the Butterfly. x920e is Verizon (and possibly Mainland China's) variant of the Butterfly.
There is a subtle difference in dimension as mentioned earlier in this post where the x920e variant is SHORTER
than the x920d.
So far, you can't get any cases for "x920d" anywhere other than Taiwanese retail and HTC stores.
Most if not all of the hard cases that are on the internet (e.g eBay), are all designed for x920e model, and they WON'T
fit the Butterflies bought from Taiwan.
If you desperately need a case right now, I suggest purchasing the silicone/TPU gel cases as they can stretch to fit the x920d variant, although you might find the sound, and some microphone cuttings won't perfectly align. However, it'll perfectly protect your case. Better than nothing, right?
Hope this helps.