Ebay, Amazon (great place for cables)
Just a quick search. You can also make one, if space is an issue. You just need a MicroUSB and a female USB. Pin 5 gets soldered to pin 4 on the MicroUSB and bam! Making one would help with space issues since you can tuck the wires easier. If you are good at soldering.
If it's just those, then I can go poke around Frys and Radioshack for one.
I don't know anything about soldering, how much is a good kit to get started? I think a friend of mine has one and knows how to use it, so I can ask him, but I realize it's something I should learn especially with the hardware mods I would love to do. If I can't find a cable in stores, or if it's special (I ask that because most employees at frys and whatnot aren't very helpful or knowledgable, so I don't want them giving me something that won't work, but if it's just those ends I'm looking for, I can do that) then I may just look into soldering my own and learning that. I see they're around $50 online but I don't want to screw myself over there.