Beagle eating grass, muzzle suggestions

We recently had to take our two year old beagle into the vet for a very expensive surgery...it was from over eating grass.

We are working on training this behavior to not happen, but it was strongly suggested a muzzle for him.

I have seen cage muzzles but I don't think this will prevent him from getting grass? We tried a soft muzzle, from Petco...needles to say it's not ideal.

I could really use some help on what to get, something that allows him to sniff, but not allow him to get the slightest bit of grass.

Any suggestions would be welcomed! TYIA!