Designed to be a very simple, more optimized way for you to fix the scale of bones that are imported with REDxEYE's SourceIO plugin, which allows for one click importing of SFM / Source Engine assets to Blender.
Source IO: https://github.com/REDxEYE/SourceIO
The script is a simple python file that you run in edit mode going UP bone chains (i.e) hand to shoulder / toe to thigh. Free but the option to donate is there if it ends up saving you some time and you'd like to say thanks.
FAQ: Why can't you just do all of the bones at once?
The Script
Open in blender's text window and run with Alt+P or the play button.
Repeat for each bone up the chain, no need to select each bone, it moves up the chain automatically.