Sure, just copy the contemporary American SIGABA machine, or the cold-war ear Russian Fialka machine. The first public-domain solution for SIGABA was published only in 2023, and I believe Fialka is still unsolved (at least publicly).

A few things that help make these secure:

1. More rotors. SIGABA has 5 cipher rotors, while Fialka has 10.

2. Irregular stepping, instead of odometer-style stepping.

3. A letter can encrypt to itself.

4. Better operational protocols.