I usually use whatever I can come up with first in one of my junk drawers. Raffia, upholstery button tufting thread, old strips of panty hose, long pieces of self-sticking velcro, and for mounting an orchid I've many times used a hot glue gun.
So it's okay to glue the roots to cork bark? I plan to try my first mounting on cork bark this weekend and saw a youtube video of someone using glue.