This might be your lucky day. There is a site that gives away commercial software, and today they have a media converter…but the version they’re giving away doesn’t convert M4P. They have an offer for giveawayoftheday users to upgrade to the full version that does have M4P support for $9.
Giveaway of the day: http://www.giveawayoftheday.com
Personally I’d load up the eval of the full version to make sure it works for you (it did for me):
http://www.daniusoft.com/digital-media-converter-pro.html
Here’s a link to the discounted upgrade: