I think in the best technical way to get through without the agents being able to detect that you have a single satoshi. The most logical would be to memorize the seeds but relying on memory would not leave me 100% at ease. Is there another feasible, safe way?
Lol. Why do you think that they will detect your Bitcoin? Unless you are dumb enough to leave your coins on a third party wallet, like a crypto exchange or a casino platform, they will not know about it.
Sure you could have trouble with your hardware wallet, if they find it and start trying to find a way to take your coins...
But memorizing your seeds is really not that bad. You just need to work on memorizing it until you can confidently say you remember.
Don't you memorize your passwords, also? So seeds should not be any different.
But to be honest you are being very paranoid. I doubt anyone will try to search your phone/laptop/whatever just to find your Bitcoin.