Change wp-content/uploads/ to media/

I have just set up my second site using WordPress MU Domain Mapping. If I upload media the path looks like

1.exmaple.org/wp-content/uploads/sites/1/… all media files
2.exmaple.org/wp-content/uploads/sites/2/… all media files

I am looking for a plugin that mofifies the I can use

1.exmaple.org/media/ all media files here

instead of

1.exmaple.org/wp-content/uploads/sites/1/…

Is a plugin for this available?

I have done some research on the net and found some hints to modify wp-config.php defining
define(‘UPLOADS’)
but it does not work, maybe the hint is for older versions or does not work with multisite / Domain Mapping.