Saw the gaylord/cardboard bin of these over-the-head masks at several area Walmarts. The unicorns went first, you cannot find them anymore. Although I saw one in the customer service area today while in the return lane. No canine types, which is disappointing. My sampling turned up bear, panda, cat, panther, shark, tiger, raccoon, and bunny.
I have seen children, teens, and adults wearing these around various stores. So I you buy one, it is recommended that it be sprayed out with a good disinfectant before you wear it. If I had to choose one now, the tiger would get my $20. IMHO it has nice color and the eyes are rather pretty.
As stated elsewhere in this thread, some of these maskimals could be combined with a pajama suit from the same store to make up a complete costume. Not a professional grade fursuit perhaps, but a start for a budding fursuiter.