So it seems to be that the tribeca front sway bar will fit the 3rd gen legacy with different end links. However there could be various fitment issues so proceed with caution. If you are running wide tires at certain offsets they could potentially rub at full lock, also depending on ride height when the suspension is fully unsprung the bar could rub on turbo cross member. Take this information with a grain of salt however because most of its just off forums.
The Bar is almost cheap enough for me to warrant purchasing one and just giving installing it a go and seeing how the fitment is.
NASIOC had this:
http://forums.nasioc.com/forums/showpost.php?p=18899839&postcount=175
Partsouq has a few of the FSB;
https://partsouq.com/en/search/search?q=20401XA00A