How about the spray called " Feliway". It's expensive but it has "feel good pheronomes" and is supposed to calm them down. Could someone else put them in the carrier and take them to the vet along with you. If I were a neighbour I'd do it for you. I've clipped claws for friends with difficult cats as well, sometimes with two people holding and me clipping. I don't mind being someone else's bad guy. Maybe there's someone to help you out. Good luck!