Have you tried getting a Subaru dealer to put out a national search for you? I had exactly the same requirements (except the colour) and I had my local dealer searching for me - but I ended up getting mine by chance (with only 42K on the clock - now just over 45K) by walking through a used car yard on the same day they got it in stock
The dealer I had searching for me rang me 2 weeks later telling me they had found 2 contenders - but they had 80K on the clock. You never know, you could be lucky. The bloke also told me that they were getting existing customers not interested in trading up to the new models due to the look of them, so the market will stay tight I reckon....one customer apparently said "the new Liberty looks like the Tribeca and the Forester have done something naughty"
Good luck with your searching.
Baz