Coping With Feline Leukemia Virus

My neighborhood has a large colony of feral cats. When a new one shows up, I gather money together to get them their shots and get them spayed or neutered. The new male cat showed up recently, but he isn’t feral. He’s grey with darker grey stripes and a bit of white on his belly and chin. He is 1 - 2 years old, healthy looking (except for a few missing teeth), likes being pet and will try come in the house (I have done this long enough to know not to let a new cat around my house cats until they are checked over by a vet). I took him to the vet today and he got the diagnosis of Feline Leukemia positive. I got him his rabies and distember shots and made him an appointment to be neutered in June. My vet says he’s still healthy so euthanasia isn’t necessary but she says he has to be kept indoors and away from any healthy cats. I won’t take him to a kill shelter, the no-kill shelters won’t take him and the feline leukemia shelter in my region is full. I can’t keep him with my healthy house cats and I can’t return him to the cat colony. I am at my wit’s end. Right now the cat is in my basement confined to a large dog crate that has his food, litter box and water. This is not a good enough life for such a sweet boy. Where do you turn to in a situation like this?