You Need: A blender jar.
You Can Use: A quart-size mayonnaise or Mason jar.

Is it cheaper to buy a whole new blender or just replace that busted blender jar? Until you figure that one out, you might try this: Many detachable blade assemblies screw right onto a mayo jar or a small-mouth Mason jar. Don't fill it by more than half, though, and as with any regular blender, avoid very hot liquids.