G/box: 70 Auto: Replacing TCM Main Pressure Solenoid?

[chuck99V70R]

Kia ora from Wellington, New Zealand.

The transmission arrow light has been intermittently going on / off for periods of time, and randomly going into limp mode from stop, but eventually evens out and drives normally after about 15 km/h (almost like it's a slow-starting manual)...

I've taken to a local transmission specialist and they've run the tests and found that the TCM-0002 error / TCM-0002 shift solenoid S1 ; Signal missing is tripping the problem. As part of the tests, and after the error cleared, they wanted to test again right after the flashing error tripped again... so eventually got it back to them and they measured the ohm resistance on all of the solenoids and they were all reading very high at 25 ohms. As such, their cautious recommendation is that I should replace all of the solenoids.

Trouble is that the "main pressure solenoid" is among the list of solenoids that they said was also reading high, and according to their suppliers is obsolete. Having spoken to Volvo reps in New Zealand, they could only order in a whole new transmission. I've been scouring around to see if I can find where to single out this particular part, but as you can see from the attached diagrams, it's not even numbered.

I can pay to have all the solenoids except for this one replaced, and risk it eventually going or causing other issues... I could replace only the S1 Solenoid, and leave the others knowing they're reading high... or pay for a whole new gearbox, which what I can find is about the same as what I paid for the car in the first palace... what to do!?

Does anyone have recommendations on if it's actually possible to order just this main pressure solenoid? Or is the only option really to replace the whole gearbox? Thanks!