I have found my cookie cutters in a variety of places. Hobby Lobby carries some and Walmart has seasonal ones out with their party stuff. If you ever go to outlet malls or shopping centers, check out the kitchen type stores because I've found some unique ones in stores like that.
Walmart and Hobby Lobby both carry a big box of 101 cutters from Wilton. And Target has a box of 101 but I can't remember the brand. I took off the label from the ones I have. But I found it in the baking section.
I order a lot of my cookie cutters online. Here are a few places that I've ordered from and highly recommend!
Off the Beaten Path
The Cookie Cutter Shop
Cheap Cookie Cutters
HB Corner Store
Hope this helps!