Ooh Walmart has the plug-ins!(technically aren't they all plug-ins? ) At $10 each I'm thinking a few could be easily purchased. I haven't thought about these in a while so forgive my excitement. They have a square one that doesn't seem to stick out too far that I could put in the mudroom for the litterboxes! Scentsationals Plug In Warmer Crown Pearl: Decor : Walmart.com
Oh stop me holy crap.