Voice over audio recording

I am looking for a voice actor to record a 40 minute narration for a video demonstration of a new cloud based business enterprise application I am working on. The intended purpose of the recording is to provide informative narration for the video in order to help illustrate and enhance the topic being discussed. The desired tone of voice is informative, not too didactic, but with an appropriate amount of feeling to keep viewers engaged and interested. Upon completion, the audio will need to be delivered in either .mp3 or .wav format.