You can use a dilution method to make your test kit read higher. It does lose accuracy but will at least give you a ballpark figure. Take one part pool water and an equal part distilled water. Mix, pour some into the test vial. Then, multiply the result by 2. If that doesn't go as high as you need, take one part pool water and two parts distilled water, then multiply results by 3, etc.

Hope Bill's eye is ok.