Hi @Jimmy J, that's messed up that this reappearance of the CH is going on right now. All too often it is only headache specialist type neurologists who know enough about CH to prescribe O2, but if your appointment isn't with one of those, you never know, you could still end up marching out of the visit in full possession of the desired O2 prescription.
CH'ers in the US having difficulty getting such a prescription have long had success just getting their O2 form a welding rentals outfit (no prescription needed, and it's purported to be the same stuff as medical O2), so you could always start looking into that, and a non-rebreather 02 mask, as a backup in case the doc visit doesn't go swimmingly.
Hey since ice in the mouth helps a lil' you might be a candidate for the breathing of freezing air that has been known to abort attacks for some of us some of the time. Bad time of year for getting any of that freezing air au natural, in the northern hemisphere anyway, but if you have a car: At first inkling of attack, run, don't walk out there with ice already in mouth, get the motor running, crank the AC full blast, stick your shnoz right up to a main vent, and breathe deeply 10 min or so until attack well dissipated. A goal can be to replace the CH with a delightfully mild in comparison 'ice cream' headache, and yes, if successful, neighbors may think you've gone mad if they hear you gleefully running up and down the street at 3:30 AM waving your arms over your head and hollering "I now ONLY have an ice cream headache!, I now ONLY have an ice cream headache!", but please do us all a favor and try to remember to have at least put on some pajama bottoms if doing so. A window type air conditioner in the living space is another potential source for the the McFreezy air.