MyArcade is preparing to launch the Atari GameStation Portable, a 7-inch gaming handheld designed to play over 200 classic Atari games. To that end, the GameStation Portable has an Atari Trak ball, paddle and a keypad, among other features.https://www.notebookcheck.net/Atari-GameStation-Portable-showcased-as-new-retro-gaming-handheld-with-Atari-Trak-ball-paddle-and-keypad.793705.0.html
If it doesn't have BattleZone and Tempest... no deal.
Centipede and Missle Command are a go, but it needs to have those other 2 classic games.
It's a little odd to say it has a proprietary OS "rather than SteamOS or Windows." You might expect either of those for a handheld PC but this is a cheap handheld that runs one emulator. Either Android or some light Linux distro like the Chinese emulator handhelds in its price range would be the alternative to something custom.