bag-ywbt via eBay offers the Accoutrements Horse Head Mask
for shipping. That's $4 below our March mention and the lowest total price we've seen. (It's a current low by $4; most stores charge over $20.) It features latex construction and is sure to generate a lot of questions if you wear it while running errands.
Note that it may take over a month to arrive. (If you don't want to horse around with that, Amazon and several third parties sell it for slightly more but with reduced shipping time.)