I've had good luck using 2 things. Goop brand sticks/holds well, and stays flexible (doesn't dry out and then crack off). But my special stuff I use to hold about anything is "windshield tape" or whatever it's called, it's a black caulking like material that is sold in flat rolls and is very very sticky and tacky and pliable with your hands. Just make sure it doesn't contact the front face of your part as the residue is very tough to get off.