Hi Pete,
We do not sell fiberglass resin.
A lot of jewelry is created with epoxy resin. Some are harder than others when they cure, so I would suggest trying another resin other than ICE resin. (For example, our Resin Obsession super clear resin cures very hard, while the Easy Cast epoxy resin can still be dented with a fingernail after curing).
You can also use polyester resin to create jewelry. This is very useful if you want a very hard cure (like it sounds you want) that can be polished with a buffing wheel.