I am in need of a good battery powered microphone that will mainly be used for ambient sound in a wedding or reception.
It will be mounted to a TRV900 so the smaller the better. It will be going to one channel of the audio while a wireless system goes to the other channel via a beachtek box.
Any suggestions would be appreciated.

Thanks

The AT 4051 is a good mic, small profile, great sound. Not battery powered though, your beachtek will need to power it. On the budget side, the Rode Videomic is really quite good too. It's a shotgun, but a wide beam, so it should do what you're wanting it to do.