I would take it to a local trusted independent - tell them the problem...
I know I often think I know what a solution is when my car has an issue - I am generally wrong!
Good luck. Love air con as the days get hotter...
I would also - generally - use the forum search facility, which is brilliant.
When I bought my car, I read every RX300 post I could find!
Found lots of nuggets!
In these strange times, my car is 'resting'.
I trickle charge the battery regularly.
Put some fuel stabilzer in the tank.
Keep the foot brake off.
Move back or forth 12-18 inches to try to avoid flat spots on the tyres...
I have read some ( Honda? ) say disconnect the battery before charging the 12v battery...
I assume this is not the case on an RX300/350?!
It sounds like a lot of hassle to do so.
I have one of these - great ...
https://www.amazon.co.uk/Inflator-Pressure-Inflatables-Compressor-Additional/dp/B07SD4GMV6/ref=sr_1_6?keywords=tyre+inflator&qid=1585818144&sr=8-6