These items have been on display for purchase at the mall, similar to the Hina displays for girls earlier this year. Like the Girls Day displays, these items are not inexpensive.
I don’t think this is connected with Boy’s Day, they just happened to be on display near the Boys Day items. It’s hard to tell from the pictures, but these are big hard shelled beetle type bugs in plastic boxes. I know cats and dogs are expensive, but I still can’t imagine having one of these as a pet.