If you feel like hacking stuff up, the FCBs for the SkyViper Journey Pro GPS and 2450GPS might fit the bill.
Also, platforms like the Matek F411 can run ArduPilot and do come in 1S/2S configurations, like the BetaFPV Beta65 Pro 1S board I have currently (though I’ve not tried ArduPilot on this particular unit).
Outside of those, I think this post will be incredibly helpful (though you’ll have to pick through the supported platforms to find 1S variants):