CCL,

I don't think he needs to be an only cat, I think he would settle with other cats but he would have to be isolated in a spare room for a significant time before introductions can even begin.

But that is good news in rehoming him. as you need to place him with an experienced cat owner who can/will be able to take on and love a special needs cat.

These experience cat owners are very likely to already be owned by several cats already.

What about doing a special write up on his needs in a honest poster with cute photos.

I did this one for Jen's cats, maybe you could write something like this....
http://www.piftails.com/main/article.../OneByOne.html

I can help if you would like me to ?

Media interest would help him and maybe your charity too.

Good Luck