This was the first thing that DS had that was "him" IYSWIM, rather than stuff we had bought him. He wears it all the time when it's cold and is distraught at the prospect of losing it when he goes skiing with the school (so much so he is petitioning my DM to buy him a different one he can take instead!)
The Buff in question is a kids polartek. It's from the Kukumuxusu range and is called Atomikao (48821) Sadly it was from the 08-09 season so is well out of stock BUT there is a possibility there is an odd one lurking on the racks in ski shops, dry slopes etc.
If anyone spots one I would be so grateful if you could let me know.
Photo hopefully attached :)