Might I suggest getting a big dog crate (I would use a wire one) and place him away from the rest of the flock? In the garage or something might work if you have space. If you needed to, you could even set it up outside a garage or something with a tarp around it, leaving good ventilation. I had to do that with some hens one time and it worked. With the cold that is coming though, inside would be better.
I would take him if I had a place, but I am full right now except the tractors that are full of snow at the present.
Always tend to him before going to the other birds and always make sure you are cleaned when you go to him. You need to keep him quarantined anyway, for both his sake and your flocks' sake, in my opinion. Whenever you bring adult birds to your flock, it is prudent to keep them quarantined for about a month to see if anything does show up. This is one reason I rarely will bring a grown bird to my property. Sometimes you just have to to get the ones you need.
That's my plan at this point. We have a sun room where I can put the crate.