Nicads are obsolescent, if not actually obsolete. If you can find NiMH cells
that fit, use them.

I've been listening to my Sony Discman at work. It runs on two AA cells. I
use PowerEx (MAHA) 2700mAh NiMH cells. In two weeks, I've gone through 16
disks of Bach organ works, seven of Hermann Baumann playing valveless horn,
and I'm well into an Andras Schiff collection -- and they're still running
strong.