Shatter resistant tea carafe/pitcher/pot
Heat-resistant glass is called for, which will be much better suited to withstand the thermal shock of boiling water than regular glass.

I'd use a Pyrex measuring cup -- which are available in one quart (4 cup) sizes, my mother owns one. (I generally just stick with two 2 cups if I need that much liquid, but that won't work for your tea steeping process.) This may require hunting through a few stores (large places dedicated to kitchen goods generally have them) or buying online. I even found a 2 quart measuring cup on Amazon, which I've never seen in a store.

You could also get a second old coffee pot, which is similarly designed to cope with hot liquid, or do the steeping in your existing old coffee pot before diluting.