Alternatively buy a rifle currently available and suitable for your purposes and which can be replaced. Insure it. If lost, replace.

I would probably use my Mauser M03 Extreme in a suitable calibre, probably .375 H&H for such a place. I believe they are available now in .458.

Insured, if lost, can be replaced off the shelf. Well in Aust, a wait of many months for the order to come through.