Agoraphobia riding the buss

I've experienced two severe panic attack episodes while taking the buss.
Now after that, no matter how aware I am that the buss is completely harmless, I can no longer take it.
There is such a strong fear associated with taking the buss now that getting on it makes me sick and trigger attacks to left and right.

What can I do to get over this completely nonsense fear?

I've tried exposure, but every attempt seems to make it worse since it triggers new attacks.

Do you have a "safe person" that could practice going with you on the bus?
Are you going to therapy? In my experience, performing exposure therapy by yourself does not work. I had to leave a job because of this.
Best wishes.