If the objects are heat resistant, glass would be an option. Or maybe a hollow glass container filled with some kind of oil with similar refractive properties. I tried to work with resin from cherry trees once. It took very long to cure and did not stay clear, but i did no research at all, so there probably is a way to make it work better.
Hmmm... Thanks for the ideas, I hadn't thought of those. Shellac is the closest thing I've found to what I'm looking for. I'm not in a region where I could tap or nab resin from trees right now. I think I'm going to have to buy something.
Beeswax has also come to mind. I wish there was some way to make it a little more durable. Like harden it so it won't easily scratch.