Ultimately, you will have to make different choices about your travel then. It isn't ideal for you but there is no chance of those trains being retrofitted with toilets anytime soon.
As someone with postrate issues, I have to plan my day around the availability of facilities. As an example, probably the most severe, is when I've a flight to catch, I can have zero intake of liquids for hours before getting to the airport as I know there will be queues at (a) Check-in - which tbh I rarely need (b) Security, even with "fast-track and (c) waiting to board in the corridor before and after ticket check.
No lounging around with a couple of beers for me!! Does make travel miserable and worrying. So if a train had no toilets for a journey of an hour or more I'm not sure I could take that train - or have to get off/on at some point thus invalidating an advance. The last bus from manchester to Bolton (60' journey) after a night out is impossible for me!! Even Bustitutions are out of the question.
On the positive side the GP has given me postrate-shrinking medication which does seem to be working making life much easier and less stressful. Anyone with the same condition should ask their GP about it!