I bought mine off ebay
for around $50, they are pretty tough to find in store any more. Nunn Finer makes a knock off called the Richland boot, but I've compared them side by side and the actual Porters are far superior in my opinion. The Richlands were quite a bit lighter and softer, and they didn't have the vented holes either. Just a heads up.
Hmanure I may have to email about yours, I'm looking for another pair!