non-rusting sauce pot for boiling water
Just use a glass pot, Corningware make some decent ones that can be used on a stove. But any glass pot designed to work on a stove with direct heat/flame exposure should work in this case.

If you are worried about uneven heating or hot spots on a gas range due to less conductive glass, you can use a cast iron or aluminum heat diffuser plate under the glass to even out the heat.