Simple Slip on Picatinny rail for Umarex Notos air tank. 
Tight enough to slide on and be fairly stable, if it must not move, slide close to where you want it and put a bead of hot glue and slide it over it.
You remove it later either by slowly heating with a hairdryer or use a syringe to run some 99% IP and that will release the hotglue. 
EDIT: a gentleman who goes by William in the Notos owner's FB group suggested golf grip tape, sounds like it would work a treat as well. use IPA to slide the print on and let it evaporate.