https://steamcommunity.com/sharedfiles/filedetails/?id=22615...By following this guide (joining the server) you'll be able to do the achievement normally (picking gifts from the ground upon fallen opponents).
EDIT: Until recently, using this method was not permitted on AStats. Now it is, and there's a better guide as well:
https://steamcommunity.com/sharedfiles/filedetails/?id=22965...This guide adds another solution: the ability to self-host a server with the plugin in question, allowing you to unlock the achievement.
As I write this, websites such as 100pals, Exophase, MetaGamerScore and Steam Hunters are currently studying and evaluating the method so do this at your own discretion. Don't know TSA's stance on this.