USB Tether Setup to pass through internet fort a ER707-M2 or an ER605?

I'm guessing if something works for that or other business class routers it should be adaptable for other devices as well.

I don't have a lot of access to USB modems, also not finding a  lot of Canadian ISP providers with Mobile Internet and USB modems.

Would be open to a few suggestions or recommendations on how to provide a fail over once the hardwired internet provider goes offline.

Thanks.