You can get E6000 at Home Depot, Lowe's, or most home improvement store. It's contact cement, which means you put it on both surfaces, wait, and then stick them together. When it cures it remains soft, but holds well when I've used it.
I've never used it on my armor but the few times I did (years and years ago) I think it dried clear. Maybe one of the HIPS armor guys will chime in since it's their glue of choice.