You can get watch batteries installed at most of the places that sell watches along Hang Gai or Hang Bong in the old quarter - especially the ones that aren't overly flashy. If you're more competent than me with a jeweler's screwdriver, you can buy the batteries off some of the street hawkers who sell nail clippers and zippo fluid and stuff.
For key cutting, I've always gone to the guys doing it tough on the corner of Luon Van Can and Hang Gai they are just down from Minh's Jazz club, in front of the soft toy sellers at the traffic lights. The keys don't always work when I've got them home, so if it is for a padlock rather than your front door, it doesn't hurt to bring it along with you to check.
answered about 3 months ago by Deano
I get keys cut on Nguyen Thai Hoc - if you're heading along NTH towards the old quarter (coming from Temple of Literature), there is a nice guy on the right side a bit before Le Duan. He sits on the footpath (in a section where the footpath is really wide) in front of some sort of sewing machine repair place. There is also a guy a bit further along, who sits on the footpath on the corner of Le Duan and NTH (diagonally opposite Hapro)...but I found some of his keys didn't work. So I prefer the other guy.
