Would you be interested in QR signing with foundation passport? We've ignored this option because if the friction of signing every zap etc, but for someone who really needs to protect their nsec it might be worth it
You could try to use a esp32 board with a screen built in like this one
LILYGO T-Display-S3 ESP32-S3 1.9-inch ST7789 LCD Display Touchable Screen Development Board TTGO Wireless Module