difficult slow feeders

for the past year or so my dog has been eating so fast that he vomits after eating so I got him a slow feeder (and been feeding him in smaller portions as vet recommended), it has helped but he still eats really fast and still throws up sometimes, just not as often. when I search for very difficult slow feeders all I can find are ones that are just as easy or even easier than the one he has. the only way I have been able to help is by handfeeding him but I don't always have time for that. I feel like there just has to be better and more difficult options for dogs like him so please give me recommendations or brands that make slow feeders that are ACTUALLY difficult and slow 🥲