Need foster care for 3 months

We found a kitten on our porch who we brough to the vet. We thought he was 8 weeks old or so but the vet said more like 3 to 3 1/2 months old. The kitten has its adult teeth. He suffers fro malnutrition but is in excellent health otherwise. The sweetest little guy. He tested positive for FIV. The vet will re-test in 3 months. There is only a 2-3% chance it will come back positive again. The thing is, it shouldn't be around other cats in the meantime. We have 2 cats now and I just had twins 4 months ago. Keeping him seperate from the other cats is not an option. I would love to find him a loving home or foster care until such time we can bring him into our home. I have pics to send for anyone inerested. I don't know what to do please ask around we need help !!