Hmm okay so I don't know a lot of OTC. Maybe a first gen antihistamine like benadryl?
What I do know is that, when it comes to prescriptions, atypical anti-psychotics might be your best bet. If your metabolism and cholesterol are fine then it can be pretty easy to talk yourself into. Well...I can at least. I don't know your situation so take this with a grain of salt.
Olanzapine (get the generic of zyprexa zydis, the melt under your tongue version) at 5mg works almost instantly for my panic attacks. A good way to start a conversation with a prescriber and start with "I have been having panic attacks but I'm scared of getting addicted to benzodiazapines. An acquaintance of mine recommended Zyprexa to me. They take it as needed for their panic disorder."
The prescriber might recommend putting you on an antidepressant (likely an SSRI), and antihistamine (likely a first gen like hydroxizine/Vistaril) or a alpha blocker like propranolol. You can argue something on the lines of "Right now my panic attacks are worsening and are getting in the way of me getting in the way of me attending work/class/other commitments. I want a guaranteed short term fix as a PRN. I'm open to taking a daily medication like antidepressant/beta blocker in addition to this."
And yes this is a great way to get propranolol if you haven't already. Before I forget, olanzapine has anti-nausea properties to boot. I'm not sure what dosage/duration you need for it to be an anti-emetic though. It's becoming more popular to use off label ataround 5mg/daily to treat nausea/vomiting in people undergoing chemo.
@CTBgenuine 's rec is good too. I know vets sometimes prescribe gabapentin for plane trips if that helps at all.