I know it is not the most popular option, but if it has to be free you can set up JMeter to run with multiple load generator instances. Put those up in a bunch of AWS regions and you have something closer to real life.
Here, I made a crappy version with comments:
http://pastebin.com/Y9F1PYLM
I also removed the light background...because I like my terminal that way - feel free to edit it back in...
