If you had provided screenshots from strokes made using that pencil, then we maybe had been able to point you into the right direction, but without such pictures most of us can’t help you with that brush, because a lot of Krita users only know that CSP exists, not how a brush from an extra package for CSP may look like.
Furthermore, you can not use CSP brushes in Krita or convert them. At best, you can extract¹ the brushtip they contain and use it as a base to rebuild that CSP brush with all its characteristics in Krita. That is in principle the same procedure that some do with their PS brushes.
But since you mention a pencil brush, it’s probably far easier to find a brush in Krita with the characteristics of your beloved brush.
If I were you, I would install the two sketch bundles from @RamonM
and try out the pencils they offer, and I don’t know if I’m promising too much when I tell you that I’m almost certain you’ll find at least one brush that’s close enough to what you’re looking for that it can be adjusted exactly the way you want it. It’s not even impossible that you’ll find exactly what you’re looking for:
SK Sketching in Krita V1
Sketch V2. (SK2) Pleasure to draw. including colored pencils and blenders
This one is also highly recommended, but for inking purposes:
INK brushes for INKTOBER 2023. Feedback.and final release
and this is another recommended bundle, but not only inking:
Mojo Moo for comics
You could also search through our category for brushes and bundles, to maybe discover your next beloved brush, but for pencils you should have ↑↑ what you search for.
Michelist
¹Here you’ll find a script to extract CSP brush tips:
To download that script, you have to click on the green Code-Button and select the option at the bottom of the opening drop down menu: Download ZIP