Confused

I would not reference time to a transponder. Use the NTP server from your network connection.
He doesn't have internet, he uses his phone for here. He could use a transponder with proper time as a start-up service with the Mio +.

I don't presently have KU capability, only C-band, so I don't know any specific KU transponders with proper time. Back when the Mio's time would keep slipping even with NTP (before EB fixed it) I was using the AFN "Bars and Tone" channel on C-band 99w as a start-up service to keep proper time. That worked perfectly.
 
He doesn't have internet, he uses his phone for here. He could use a transponder with proper time as a start-up service with the Mio +.

I don't presently have KU capability, only C-band, so I don't know any specific KU transponders with proper time. Back when the Mio's time would keep slipping even with NTP (before EB fixed it) I was using the AFN "Bars and Tone" channel on C-band 99w as a start-up service to keep proper time. That worked perfectly.
I've had good luck using the French transponders on 34.5W Ku and i think also with the PBS mux on 125W