I haven't heard of any glue for packers - only for prosthetics, which are made of silicone while most packers are made of cyberskin (except the mr. right and two others the names of which i cant remember). The glue will most likely ruin your cyberskin packer (been there, done that), because cyberskin is porous....and a diva.
So, you could either glue on the Mr. Right, which doesnt have a tab, so you'd have to glue it on further up than where it would naturally be attached--- i tried gluing it on where it should be attached and that's certainly not recommended (removing glue from labia - no fun).
Or buy a prosthetic.
Or find another way to keep your packer in place. I personally use boxerbriefs (i buy mine at H&M) and cut two holes through the inner layer on the front, like in this drawing:
http://farm8.staticflickr.com/7161/6602516083_f4e7a2c429.jpgNo harness, dick is secured in the right place and can't fall out or spin around in my boxers.