I've been in the very same situation. Hurts like hell. I've sworn "never again" but always succumbed to the desire to have a furry little buddy in the house.
The last time I lost my best friend, my daughter actually made a great suggestion. Go to the pound and pick a "last chance" mutt. The uglier and scragglier the better. My reply to my daughter was I don't want another dog, especially one that might only live another year or two. Her reply was that at least I could make the dog's last year(s) the best the dog has ever had.
Well, my last chance little buddy has surprisingly been with me for 5 years relatively health issue free.
You can never replace your best friend; just like you can't replace a child. But you can make a new friend!
Hang in there brother. My prayers are with you and yours.