How is Boots now? I had a thought, sometimes cats just like to eat some grass to settle their tummies. A vet told me a long time ago that sometimes bits of indigestible stuff gets stuck in one of the loops in the intestines (gut) - like a tiny piece of bone or feather or insect outer shell. They will keep trying to shift it by vomiting. Let him try to eat some grass. My cats don't have a garden with grass but I keep a big pot of Catgrass on the balcony for them and they visit it almost every day before or after breakfast. The act of vomiting helps to make the gut squeeze its contents along. (This works in humans too, by the way, if ever one has those difficulties, to make oneself vomit helps). They will just throw it up (on the carpet, usually ) -cats I mean not humans, lol, then they feel more settled. You can buy Catgrass at nurseries, it will be in with the other kitchen herbs like parsley etc. Not expensive, about A$3-4 in Australia.

The vet I go to now, sees only cats, and he said some cats are just chuck-uppers. Every few days they can't keep anything down then they are fine again.

However it is always wise to get a cat checked over if there is anything out of the usual behaviour happening and some of the places the other people told you about might be able to help you for a few or no dollars.

Here's wishing you and Boots luck.