Yes, I have the M10 score put out by Faber Music from London, in collaboration with AMP of N.Y. City (Associated Music Publishers Inc.). I believe that this is the second Cooke edition, as it gives credit to Colin and David Matthews, who added more useless filegree. This score does, in fact, an outstanding job of comparing what Cooke and co. did, in comparison to what Mahler left. In many places, that means little or no differences. But in the last two movements, this becomes a far bigger issue.
I really don't know what else is avaialble on M10. I believe that there might be a score available of the excessively orchestrated - and not terribly idiomatic sounding, I might add - Barshai score. The beauty of Barshai's work, is that he's cleaned up a lot of - what are believed to be - wrong note mistakes that are still in the Cooke version. The problem is, Mahler's writing is so difficult to decipher, that it's often times near impossible to determine what notes he was truly wanting. This is especially true when he's writing many ledger lines above the staff. Mahler was also inconsistant about carrying over accidental markings (I'm getting a bit technical for those who don't read music). Needless to say, Mahler was greatly distracted during this period of his life. In addition to this, I believe that Barshai - or somebody else - may have published a version which shows only what Mahler wrote, but with Barshai's corrections. If that's available, that may be a great place to start. I'll try to Google this topic, and see if anything comes up.