I've got a pair of walls that have a button flap over the zipper and they are cheaper than carhartts
Berne was made here not sure now. Some have snap over flaps and some don't in Berne brand but cost less too.
Look on Dungarees .net they sell everything Carhartt makes. They have coveralls and overalls that you can find in most stores , might have something that will work for you.
I wear Carhartt bibs with the wind flaps. That keeps the zippers pretty safe,
hey boss, here is a site that might suit your needs, www.devvy.com/made_inthe_usa.html. it is a compolation of american made product web sites. youll have to look around a bit but it might help.
Levi