You can calculate a spherical-only prescription from an astigmatism prescription. Order cheapest-possible glasses using those lenses, and wear them for a while before visiting a new optometrist. Leave them behind before you go in, and say you lost your glasses in the ocean, or they got crushed under a truck tire, or something. If you end up with a prescription that has a cylindrical component, and it has the same axis and magnitude as your previous prescription, then you have an objectively-measured, independently-repeated astigmatism.