Only rug I have found to keep a mane in full flow all winter is the Rambo Duo. I use them on all my boys and they all have full manes. Not the cheapest rugs but the cut of them is lovely.
Is there a good place to get MTG? Having had a quick look online the cheapest I found was shipped from the US and genrally ranges in price a lot! Even without wearing a neck cover PBs mane has gone very thin at the bottom