Depends on why it has runout.

Often internal damage (or debris jammed) inside the chuck. That can be as "simple" (often not so simple) as disassembling, cleaning, and/or filing/grinding away the offending defect, then reassembling; depending on what's going on.

That is: "not bearing runout" which tends to be pretty hard to spot unless it's extreme. It's also your most likely to be "reasonable" repair effort.

Otherwise, you have only a couple of actual bearings. It's hardly ever cost-effective to replace the bearings rather than the whole tool, in part because they can be difficult to find, or the part of the case they mount to may be damaged, rather than the bearing itself, or the worn bearing may have caused damage to the motor by letting parts slop around and hit/scrape each other.

Depends on why it has runout.

Often debris jammed (or internal damage) inside the chuck. That can be as "simple" (often not so simple) as disassembling, cleaning out the debris, (and/or filing/grinding away the offending defect,) then reassembling; depending on what's going on.

That is: "not bearing runout" which tends to be pretty hard to spot unless it's extreme. It's also your most likely to be "reasonable" repair effort.

Otherwise, you have only a couple of actual bearings. It's hardly ever cost-effective to replace the bearings rather than the whole tool, in part because they can be difficult to find, or the part of the case they mount to may be damaged, rather than the bearing itself, or the worn bearing may have caused damage to the motor by letting parts slop around and hit/scrape each other.