You will be the seller so you will have complete control over who you sell him to. Place an ad online that gives prospective buyers the full run-down on him. Leave nothing out. If someone has interest in him, let the prospective buyer meet him and again, be totally honest. If you want the perfect home for him, you might have to be patient. This is what helped me through selling my first horse. I felt very guilty. It helps to remember that you are in control of the situation and you don't have to sell him to someone you're not comfortable with.
Having people tell you not to feel guilty doesn't always help but try to think of it as making his life happier by fitting him with his perfect human companion.
“Out of suffering have emerged the strongest souls; the most massive characters are seared with scars.” -Kahlil Gibran