Written Option 1:

The Knights would probably go for an animal that can protect those in need and be an overall great being with a big heart.
I'd say a dog, maybe a German Shepherd would fit this criteria. A fitting name would be Lancelot.

Lancelot would be around during recreation and tactics meetings (well as long as he can stay quiet during them haha). They would be a mixture of emotional companion, playing buddy, cuddle friend and so much more.

Maybe we can buy him a little suit of dog armor so that he looks the piece.

Another idea would be a glorious hamster. Those can always pnuch above their size and would look hilarious in a little suit of armor.

Anythings but cats really, those are too devious and evil to be an honorable knightly companion. They would probably rather stav you in the back, the moment they feel like the Maine Timber would feed them more Tuna than you.