My students have a pen and ink project coming up

I’m not a trained art teacher, I have a GCSE in art from the late 80’s when teachers didn’t teach you anything they just told you to do stuff. Anyway, I have a pen and ink project coming up with my grade 9 students who are going to use their name and create zentangle designs around it. What’s a decent type of pen that they can use that is fairly inexpensive? I usually end up buying all our art supplies because it’s easier than trying to get my school to reimburse me. Can they just use a thin sharpie or a regular black ink pen? What do you think?