The best glue for gluing of any kind IMHO is called Hxtal-NYL 1. You
can find it at http://www.ganoksin.com/gnkurl/37
I learned about this glue while in school, and one of the most
promising things it has going for it is that it is archival, so it
will not harm what you are using it on, is NOT sensitive to light
like most of the epoxies are and is said to last for 100s of years.
It is used as the number one adhesive for museum restoration. I have
used it many times, and it is simply a wonderful product. It was
originally developed to match the refractive index in glass and
actually will seek out cracks and fill them nicely. I actually saved
al alabaster sculpture during carving by filling in the week cracked
areas with it and letting it sit for a week. I was very surprised
how deep the adhesive actually moved into the sculpture while
finishing the carving, probably about 3 inches.
Now, as far as allergies to epoxy go, this is a 2-part mixture glue
(many of the best ones are), but it is not made with the same resins
as epoxy and it is mostly odorless. It is often used for ceramic and
glass, though I have had wonderful luck using it with stone, wood,
bone and fossil ivory. It is a little expensive, but can be ordered
in smaller quantities. For mixing, you get the best results if you
can possibly weigh the two parts as you mix them. It DOES take a few
days to set properly, although that process can be rushed a little
bit by the use of a warm hair dryer.
Hope this helps,