5V 2A is the traditional 10W "slow" charger. Basically any wall charger should do that, only a USB-A port (or a broken charger) will be less powerful. So if you have one of your old chargers and a suitable cable (USB A to C) that would work. According to GSMArena the Moto Pure only does 10W charging, so no point paying for anything fancier (though a good charger should also be able to output that if it detects that's what the phone wants).
If that message only appears when the charger is plugged in though that implies that it thinks the charger is not a charger. Which means either the charger, the cable or the phone's USB socket is broken. If you have another cable, try that first.