I don't know about the specimen itself, but glycerine is (I believe) classified as a hazardous material, & as such, most likely won't be allowed on the plain with you. I'd be wary of opening the container & putting it in a bag with wet paper towels too, especially if there's any chance that it's not glycerine, but some other toxic chemical. If it was prepared in China especially, I'd be cautious about exposing myself to its contents. Shipping is probably the safest way to go, but it's most likely not going to be a cheap undertaking. I had to order cesium from the UK once several years back, & it required at least one certificate from US customs to import, one from the UK to export, then once here ANY hazmat requires a special box & metal container peDOT regulation for transport. & that's just for the preservative, I'd recommend doing your homework about the animal itself. You had mentioned it was from an artist; have you checked any scientific supply houses for a reasonable facsimile? Your whole effort may be impeded if this unit is put together for show in some "artsy" vase, & not a container 'built to spec' for housing such a sample. Good luck to you, I hope you can get what you want affordably.