You can usually find that kind of thing pretty readily on TurboSquid or Content Paradise.
There's also quite a few resources for free mocap data if you're looking for some general animations just to play around with. Try one of these:
http://mocap.cs.cmu.edu/
http://www.mocapdata.com/
http://www.animazoo.com/Free_downloads.aspx
Most of these motions are usable by human characters of average proportions.
I don't think there's a BVH importer for AC3D but since a BVH is a text format and you're only looking for 10 frames or so, you can probably import it by hand. Open the file in notepad or your favorite text editor. Each "channel" line in the file represents a rotation on the X, Y, or Z as specified. If you start at the end of the chain, i.e. such as the hand, and then apply the rotations it says in the file working upward to the pelvis, you should be able to re-create the motion in AC3D. It would be a bit of a pain, but do-able if the animation is short enough.