You can design your own logo and then make it into a stamp for your sketches. I found this graphic on making a “hipster logo“. The graphic makes it look easy, but it does require some image editing skill.
I’ve had my own logo, or maker’s mark, for decades. It’s the crowned Irish harp (see “about” above). I had a small red stamp made and sometimes stamp my sketches with it. You can see it on this sketch:
It was really fun when I was at an Urban Sketching workshop in Portland to stamp the sketches done there with a “Made in Portland Oregon” stamp that someone brought. See bottom of this sketch.
So I used that hipster logo graphic to design another one. I used Publisher and Photoshop Elements for the image creation and manipulation. Then I uploaded the image to an on-line company that makes rubber stamps. It came today. At 1.5 inches diameter, it’s a little large with which to stamp my sketches but I’ll use it for backs of cards, first page or cover of a sketchbook and other things.