The recommendation below is an advertisement. Most of the links here are part of Amazon's affiliate program (unless otherwise stated), which helps support this website. It's also more than that - it's a hand-picked recommendation of something I've used myself. If you're interested, here is a full list.
Faber Castell PITT Artist Pens
Like the Staedtlers, these also come in a set of multiple weights - the ones we use are F. One useful thing in these sets however (if you can't find the pens individually) is that some of the sets come with a brush pen (the B size). These can be helpful in filling out big black areas.
Still, I'd recommend buying these in person if you can, at a proper art supply store. They'll generally let you buy them individually, and also test them out beforehand to weed out any duds.