I refinished some old OEM caps where the crest was falling off, and I used body emblem adhesive to hold them on, and so far they haven't fallen back off again.
https://www.amazon.com/3M-03601-Plastic-Emblem-Adhesive/dp/B000CCM3J2/ref=sr_1_1?ie=UTF8&qid=1486763909&sr=8-1&keywords=body+emblem+adhesive
If you use this, be very careful not to let stringy tails come off after you squeeze it out, it sticks everywhere... I'm also using it to hold a hook onto my shower wall for my shaving mirror after it kept falling off with various double sided tape attempts.