Which cheap midi controller could work as USB host for the Mojo61? You will need to use traditional midi connections.
I think you got it backwards - you'll want the Mojo61 to be a USB host, and that what it is, one of the very few keyboards with this feature.
Well in that case this is a hidden feature of the Mojo61, Crumar specify it like this:
USB Type B for MIDI IN/OUT
USB Type A for software updates
Also checked by connecting a Yamaha CP4 USB B to my Mojo61 USB A, no luck.