When I first started I didn't see much that could be done either. But then I discovered the JDM aftermarket and there are tons and tons of things for the Legacy that they just don't share with the rest of the world. I'm very lucky to know someone who can tap that JDM market for me.
But you're right. To me they seem pretty much similar. I think as of 2007 in Australia and 2008 in the US (when the face lifted models came in), Subaru started to be more standardised. Grills that were once different are now shared with the 2.5, GT, and GT Spec B. So I reckon the ZeroSports front lip should fit the USDM model for your year as well.
The vendor I get my stuff from does not ship international, however I checked the JapanParts.Com website and it looks like the sell the ZeroSports front lip now (it's called front under spoiler). The price itself seems reasonable. But what will kill you is the shipping. Because it's a thin piece of plastic that takes up a great deal of space and cannot be folded, it's shipped in a huge wide box (albeit thin).
I am absolutely in love with your car! I have an obsidian black 08 Leggy... I see so much potential now! I do have a question for you - The Liberty and Legacy appear to have a very similar front bumper cover... I'm wondering if the front lip that you have will fit my car! I'm willing to take the chance so would you by chance tell me where you got it? Thanks so much. You must be proud!