Well, you could always grab a cheap bucketfull of regular game dice, shake them for a few seconds in a container, then dump them on the floor, take a picture of the floor with the dice, grab the raw or jpeg file, and get it's SHA256, use that result as the private key (or as input to another generator).

Might be overkill, but it's fun. And you'll only need to do it once.

Personally, I'd just use the bip39 page and click on 24 words a few times, then save the extended private key somewhere; maybe make a few more. At least those can be loaded into most hardware wallets and Electrum.