Well, you seem to want hardware you can trust, but say that you don't trust any of your hardware. So, you need to get your hardware into a state where you trust it, or you need to acquire new hardware that you do trust. Something like a Raspberry Pi may be great for this sort of thing, though on "embedded" kinds of devices you want to make sure that your random number generator has enough entropy to work with.

Or to be completely offline, you can flip a coin 256 times to make the private key and have a calculator and pencil and paper to calculate the public key and address. I want to do it one of these days just to show that it's possible.