However, if you want a mask of your own, you ought to get on it. Shops across Philadelphia are struggling to keep masks in stock and, as you can see above, they're selling out on Amazon and at Walmart. That's led some suppliers to scramble and it's forced an increase in prices, according to ESPN.
CreepyParty, the company that made the German shepherd mask worn by Long, sold out of their stock and even has a note on their site about their supply issues. The company expects to have more available for order starting on January 25. It is also guaranteeing that you'll get your mask before the Super Bowl.
Though that German shepherd has been sold out, you can still find a lot of masks on Amazon that are in stock. (And here's that poodle from the image above.) There are also places that aren't Amazon, like Archie McPhee that carry latex dog masks. However, shipping and other details vary from site to site, so make sure you know you're getting it in time to bark madly at the TV.