If you want a vegan pet, consider a rabbit. A friend of mine has two larger buns who have the run of part of the house just like cats might, and while they do need a bit of different handling (you have to be very understanding of their boundaries and get *consent* before petting them or they get stressed), they're perfectly fine pets that don't need to eat meat.

(Herbivores in general require different handling because their instinct is to see us as a threat and we have to make it very clear to them that we are Not Going To Eat Them).