I don't know of anything that fits your requirements. But, if you don't mind a tangent, it appears that Pokémon: Infinite Fusion has both Windows and Linux releases, would it be acceptable to run it under one of those OSs and use the applicable version of the application? There are a lot of Linux based handhelds on the market, and it should be possible to find something which works for you using Linux.
Gaming Handhelds
A place to discuss, show-off and share the love of handheld gaming devices.
I thought about it, but it seems like battery life would be worse and the resulting device itself would either be bigger or more clumsy (e.g. Steam Deck for the former, GPD systems for the latter)?
I have a first generation Framework 13 mainboard I could hack into my own version of a Steam Deck if I did go that route.
That's not to say I'm not open to suggestions though.
There are a lot of Linux based hand-held devices which may be a better form factor for you. For example, something like this (I have not used this device, just picked an example) might not be a bad fit. At 12cm on it's long axis, it's not terribly big, and lacks a joystick. Looking out at reviews, the battery life seems to be in the 8-10 hour range.
Others in this community may have other, better recommendations. But, there are a lot of choices in this area. I recently bought two of these for my kids for Christmas. And after playing with them to set them up, I was impressed for what it was, at the price point it was offered.