How to add private messaging in BBPress

Hello,
I would like to add a private messaging system to my BBPress forum. I am looking for a plugin other than BuddyPress because I do not need everything BuddyPress offers. The plugin should be easy to use on the front end, and integrate with BBPress easily. Ideally, it would be nice if there was a button that a user could click on to send a message and the To: field would already be filled.

Please let me know what you can find, my search turned up a few, but I need some BBPress ready plugins.

Thanks again. :slight_smile: