I purchased a 100m drop proof and water proof 16gb USB 3.0 drive, for this sole purpose lol.
Wouldn't recommend safe though, I would recommend hiding it. People will expect to look in a safe, if you are literally that worried that someone will break into your house and make off with the safe and your wallet file, why not just put a fake wallet file in the safe and hide the original somewhere else, in the lining of a jacket, or under a molding panel.
I agree most small safes that people use in homes are really only good for light security and fire protection of important papers (insurance, wills etc). Often most home owners don't even do a good job of bolting down or hiding these small safes and the crooks take the entire thing and crack it later.
If you are going to hide it securely in your house make sure it's in a place that will survive a fire or other disaster.