Ink Question

Hi all! I'm hoping someone might have advice on finding an ink to refill emptied Uni Ball pens. I have a handful of Uni Ball micro pens that I like the feel of but have used up the ink in. I'd rather not throw out what are otherwise perfectly fine pens if I don't have to. While I've dipped my toe into the world of fountain pens (I have a Kaweco sport that I use with increasing frequency), I'm worried that just any random ink I pick out will bleed too much in my lab notebook. I know the Uni Ball pens are not fountain pens, but does anyone have advice for ink I might be able to use to refill them? Or inks that are less likely to bleed on cheap paper that I could put in a pen I'm not attached to yet? There are some sticky fingers at work so I don't want to take in sport since we've bonded... I'm looking for something similar to the black or blue that came in the pens. My sport currently has Kaweco "Royal Blue" ink in it, which is more purple than I like and part of the reason I don't use it all the time. Thanks a mill!