Megs36 I hope you outlive your lovely cat. If not, I hope that someone takes him in. I know that one of the cat charities will guarantee to find a good home, if necessary, if you give them a donation.
My next door neighbours are 'bereaved' regularly. They adopt elderly dogs whose owners have died, or gone into care. They have two young setters of their own, so they do two or three 'energetic' walks with them each day. They also do a couple of gentle walks with the 'old dodderers,' as I call them. They are a wonderful couple. Most of their time is spent caring for all of the dogs. They give them all lovely end-of-life care, which may only be a few months, and grieve for each one when it dies.