I may have some pint bottles of low odor tabletop epoxy. I ran across them when moving, but can’t remember if I kept them. I’ll dig around a bit today and see if I can find them. If I do, you can have them.
Even if you can find resin that is low odor/non-toxic, you're likely going to be sanding it down which is gonna make a mess of tiny particles that will fly through the air and take a trip into your lungs. I know respirators can seem like a big spend but consider it an investment for your health in the future . I know that I find if I do some light sanding with really fine dust without a respirator, my throat starts to burn so I need to chug down a litre or so of water to flush it out (this isn't an OK alternative for a respirator, I shouldn't actually be sanding like this without one).
Looks like 15 years of Texas heat rendered this stuff unusable. The resin is like thick tree sap and brown yellow.
Ditto on the above. My epoxy work is small stuff (knife handles) in an open garage. I’m not concerned at all with organic vapors. Cleaning stuff with xylene or acetone, on the other hand, I use one. I wear one for all sanding whether it’s wood, antler, steel, or nasty carbon fiber. No dust is good for you. $25-35 will get you a good one. I like the 3M 3000 series. Easy to find filters for them.
If you really need something you don't need a respirator for, you could try PVA glue. It's not super rigid and not water resistant, but it can be a start, and it does harden it a bit. To get it more rigid, try adding some kind of matrix.
Worth a try. I know some people use wood filler on 3d prints because it's less toxic than bondo. I'd probably start with some glue on the outside though as it should make it easier to then cover the inside. Adding some fiberglass or fabric on the inside would probably increase the strength a good bit too.