Here's a little tutorial on how to make your own rubber stamps. I like to use a stamp carving block as this allows you more freedom with the size. It can also be nice to affix your stamp to a woodblock to make stamping easier.
DIY pencil eraser stamps: What a great simple idea! I was trying to figure out out to save cost for a logo stamp of my upcoming jewelry line, et voila! still one of my kid's big pencil with eraser and do it myself!