At the moment i can't even find the 3.5mm version, this version can be used with an adapter:
The Pyle AA version:
Not a widespread problem, but...Most cameras can provide the residual power needed for mini microphones through their 3.5mm port, but some just can't.
Don't confuse this for phantom power, that's something else entirely, and this isn't an issue if you have any sort of powered microphone. But some cameras, like the Canon C100, have completely passive 1/8" mic ports, meaning you can't plug in something like a laptop mic into them to get scratch audio.
I searched a long long time for a solution, and there are very few. If you have a particular mic that you want to use which doesn't have power, the above listed solutions should work, and are very inexpensive. They just put a battery capsule between the camera and the mic, providing the needed power. Another solution is to just get a small, powered microphone.
Again, if you're just looking for scratch audio and want something as small as possible, there's a very limited selection. The one i ended up with which im overall pleased with is the Bronstein mic, which is reviewed here: http://www.mediahalo.com/articles/bronsteinmic/