Just a thought, but maybe the easiest would be to get a .375 H&H Mag. Seems like a fellow can sometimes find one that a guy bought and then got scared of.

Anyway, since action work might add up quick for cost for some other caliber, a .375 H&H barrel should be able to be replaced with a .300 H&H and you should be golden. I don't think any action work would be necessary, and obviously the bolt face would be fine.

Just an idea.