Brother,
Only 30~40% petrol stations keeps Hi-Octane. Mostly pumps keep CNG, Super & Diesel. So dear, you have search out by yourself.
As far as filling from one station is concern, unless you will not change the station, how you could know that (others) fuel quality is good or bad ??
Hope you are wise enough to think what you are going to do next?
Cheers & LOVE.