I got this awesome stuff from home depot a few months ago. It's a soft blue rod with a white center. You cut off a chunck, mix it with your hands and it is the consistency of putty. Well, it is putty. place it on or in what you want to use it for and in 15 minutes its hard as brick and stuck in place.
I would use this along with a bolt to fill the center with a bolt in place to make the hole. when it dries, back the bolt out. Viola...instant filling. one tube was like 5 bucks, and I've used it to mount standoffs, hold nuts in place, and repair a hole in the vacuum cleaner tube.