OMG, that's so scary. I would contact a compounding pharmacy and see if they can do an epi pen for you. A lot of my dog meds come from a compounding pharm bc vets often don't carry the potency needed for our little kiddos.
Call Diamondback Pharmacy - this is where I get my meds, and some other folks at YT do too, bc they ship nationally. If they *can* make an epi pen, then your vet could call it in for you and they could ship it to you. Here is their website:
Diamondback Drugs - Veterinary Medicine and Compounding Leaders