If it is only glued up 3M Super-Adhesive Spray http://solutions.3m.com/wps/portal/3M/en_US/3M-Super-77/Super77/?WT.mc_id=www.3m.com/Super77
Not cheap but should do the trick. I used it on the sound pad under my bonnet (hood) on my MGB over 8 years ago and it's still holding.
I'm assuming there is some metal behind the insulation to glue it to.