If not offensive to you, it may be possible to remove the SIM card and use it in a MiFi, assuming you've got a good price/rate for your connected-car plan and your cellular carrier doesn't care. For a time, ATT sold a Mobley device (OBDII) and that unit has a removable SIM. The connected car plan at $20/mo + taxes and fees was considered a good deal for "unlimited data." "Unlimited" in that case meant ~20Gb at regular speeds. Anyway, during the ATT Mobley time-period, folks were able to move the SIM from Mobley to a compatible MiFi device.
Oh and re-reading your last note, maybe this is what you mean by travel router.