All kids seem to go through the fear of monsters stage; Bedroom monsters, toilet monsters all kinds. So here's something you can try; Monster-off Spray and Monster Free Zone signs.
Feel free to print these out (copy and paste into word or PowerPoint or save the images) and use them. I recommend printing on card for the sign then laminating if you have one of those contraptions.
Photo-paper stickers work well for the monster spray, stuck onto either an empty spray cleaner bottle or a fresh one in an appropriate size bought from your local hardware of garden supply store (some pharmacy's even have them.)