Wireless joystick or keyboard encoder?

[wrybreadsf]

I've built a few MAME cabinets over the years, always with a regular desktop computer, but I just made an interesting discovery: a Chromecast with Google TV (a $30 Android TV gizmo) runs old classic 80s arcade games via MAME really well (with Mame4Droid and RetroARCH). I'm currently using a bluetooth XBox controller, which works but not having a 4-way joystick for games like Donkey Kong is a serious deal breaker, and that's the kind of games I want to use this setup for. So I'm thinking about building a little portable controller.

Out of the box the Chromecast doesn't have any USB ports, and though it is possible to add them with a dongle I'd rather just keep things wireless. Does anyone happen to have a recommendation for a Bluetooth keyboard or joystick encoder?

Or I'm seeing various Arduino type device that can be HID devices (like a keyboard). Do any of them work well enough for MAME? (In terms of reasonably low latency and simultaneous key presses).

And any recommendations for a joystick that can be switched between 4-way and 8-way without opening the controller enclosure?

Or maybe I'm overthinking it and there's already a good off the shelf wireless controller that people recommend? I see the 8bitdo stuff recommended pretty often, but there doesn't appear to be a 4-way version.

[jeremymtc]

Why not use a donor PCB from another Xbox wireless controller? Just solder your button and stick wires to the pads on the pcb and voila.