Foam adhesive tape! Where I'm at it's advertised to hold up posters and the like, but it perfectly replaced all the backing to my abode sensors when I moved. Here's something similar to what I bought:

2 Rolls Double Sided Foam Tape White PE Foam Tape Sponge Soft Mounting Adhesive Tape (3/4 inch by 50 Feet) (1/2 inch by 50 Feet) https://www.amazon.com/dp/B07DWX1NN9/ref=cm_sw_r_cp_apa_i_jed8DbV8YHH59