Bald klingons are actually pretty common, but not in TNG, Voyager or DS9
We see this charming fellow in the reboot film Star Trek (2009)
General Chang from the Film "Undiscovered Country"
And this bald(ing) chap in a background shot in The Original Series
Moving down the canon scale, we also come across hairless Klingon warriors in various trek novels
“What’s this offal?” the bald Klingon groused, sweeping the
accumulated padds and isolinear rods onto the floor. He stalked away
from the workstation, trampling the fruits of Picard’s labors under
his feet. “I should have known we wouldn’t find anything worth taking
on this miserable ship.” - TNG: Glass Empires
A bald Klingon appeared, bowing before the Regent. The port officer was scrawny, with dark overhanging brows and a long, thin mustache
drooping from the corners of his mouth. "Greetings, Regent Worf, on
behalf of Khitomer You are cleared to maintain your current orbital
altitude. You may beam down to the spaceport at your convenience."
DS9 : Dark Passions