http://www.hpcgears.com/products/helical_gears.htm
there must be a company like this in the US - they make and stock plastic gears - just make it from nylon 66 or delrin - i would guess about 20 bucks tops.
or take the broken gear to "a.n. other engineering company inc." and ask them to make you a new one - or a dozen and sell 'em on here
