You can setup the trezor without any passphrase too, simply by letting the password field empty.
And instead of buying a second trezor, writing the passphrase on the backup paper of the mnemonic code would also be a viable (and cheaper) option.
that's what I am thinking, one trezor and a mnemonic passphrase. I see they have two models available just need to pick one, also the cryptosteel gadget is really cool, a little pricey but still cool