Do a good long pour of boiling water in the v60. Make sure it’s hot to the touch. This won’t eliminate temp drop but at least help.
Another question: is it a glass v60 or plastic? The plastic ones work much better at keeping the temp counterintuitively.
Morbid but with the amount of school shootings that have happened the more people that can call 911 the better. The kids need the phones to possibly save their lives. Signal blockers are not the answer.