grip
I've got two tricks for slick knives w/ slick grips.
One is to simply wrap the grip with a rubber band, or you could cut a small "o" section of bicycle tire tube. Goofy looking but it works,but typically will not hold up.
This trick has worked much better for me, and looks OK too. Friction tape. The product I'm using is called "Skid Guard" safety tape. It is adhesive backed, can be cut to shape with scissors, and will generally stay where you put it for a long time. Now that I have some, I find other uses too, like on treestand steps and platforms, step bumper of my pickup, anyplace you need some "sticktion". I put a small strip on my early Glock pistols as well.
I put two, 1X 1/4" wide strips on the top and bottom portion of a Cold Steel Canadian belt knife, and it really brought that handy blade to another level. I can't recomend you try it enough.