You don't need a peroxide test from Merck, just put a little of the ether to a test tube with a bit of aqueous iodide salt (KI, NaI), mix the layers and when you see the purple color of iodine in the ether layer you know your ether contains peroxides. Also, starch makes an intensely blue complex with iodine, so adding starch to the mix makes the test sensitive as well. This could be applied so that you could make a tester strip yourself. Haven't made a tester strip this way, so I won't give a method because I haven't tested if it would work or not.