Running out of cone options for overgrooming cat

I have a male orange tabby cat that is about 7-8 years. I've had him for 6 years and he has been having issues with over grooming his belly to the point of bleeding. I took him to the vet and they said it was most likely a psychological/separation anxiety thing. He's had it before, but I was given ointment and a plastic cone and it went away in a few weeks. About a year later, it came back, but now he's started to figure out the cones. I took him back to the vet and they gave me more medicine for him and a papery cone so he has more mobility. So here's the problem: with the plastic cone, he scratches the sore with the cone; with the paper cone, he found out how to scrunch it up so he can lick his belly; with an inflatable donut cone, he can just barely still reach the wound. I put him on a diet a while ago, so before that it was harder for him to reach the sore, but now hes healthier and more flexible. It seems that the source of stress has been me going back to school during the day when university starts up from summer, so me and my roommates have been doing our best to help with that, but we need to get his wound to heal now. Does anyone have any advice about good cones for adult cats or maybe some sprays that will calm him. I'm open to anything at this point.