I was wondering if there is such a thing as a high-speed MicroSD adapter. I ask this because I use a class 3 microSD when I'm recording 1080p video, but since I've been doing this, my camera's on-board cache fills up forcing the video to stop recording.
There is no such thing; the adapter simply translates a copper connection between the mircoSD format and the SD format. It has no logic of its own and therefore will simply be as fast as the card you put into it. However, there are faster cards available.