Beacon Adhesive's Gem-Tac is a premium quality adhesive formulated specifically to secure gems and rhinestones.
 
One of the only adhesives that is suitable for applying mirror backed stones as the glue won’t warp or alter the appearance of gems or rhinestones. It dries crystal clear and is made from a safe, non-toxic formula.
 
The bottle tip is very fine allowing for precise application meaning this 5ml tube won't break the bank but will last surprisingly long as you only need to apply such a tiny amount.