Nice clean looking bike, engine looks very well
Is there a tear on the Seat?
If not, spray it liberally with WD40 and just wipe of the excess and leave it dry into it over night.
Do it once or twice and it will keep it supple.
I have treated many seats including my own. Once the WD40 dries in it won't be any more slippery than it is at present.
Son of a Gun is another option but I have found WD40 better as it is less slippery when dry.