Buy this phone:
https://www.argos.co.uk/product/3181658
You don’t need a sim card in it. Connect it to your home wifi. Log in with a Google account (create one if you need to) and put your season ticket on it. You can pass it to whoever needs to use it.
Costs same as paying to share...
Some info in this page:
https://support.google.com/android/answer/13658562?hl=en-GB
Including how to do a manual scan:
You can check for trackers that are separated from their owners and currently near you at any time.
On your device, tap Settings.
Tap Safety and emergency Unknown tracker...
Wardens in Brighton check numberplate to see if driver has paid by app. If you have a permit it shows up in system. The adhesive for my permit went crap and the permit was in passenger footwell for a few weeks but no tickets in that time.