Hi. Welcome to Just Answer.
You need some "Gorilla Snot"! It sticks well to plastics and will adhear to the rubber magnetic tapes as well.
Ok so you cant get the gorilla trainer to get some for you. In that case just use some 3M weatherstrip adhesive. It comes in yellow, and black. It is very durable and weather proof. It even holds up in caustic environments, like sea salt and battery electrolite.
I use it for many things. holding sand paper on my orbital sander, gluing down stubborn formica strips on counter tops, patchig my rubber boots that I use for pouring concrete, it makes a great substitute for patching rubber tire inner tubes, glueing leather and cloth to just about anything, gluing tail light lenses that were damaged in a fender bender back together, gluing same tail light back to vehicle, and even gluing a rattle snakes head (well desicated) to the top of my monitor.
You can get it at any hardware store or automotive parts house. It costs about 8 bucks for a tube of it.
Please let me know if you have any other immediate concerns.
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Yes Im serious about the rattle snake head. =)