What a beautiful cat, and great companion as you describe. My orange kitteh and best friend is now almost 17, and so far he's hanging in there though showing signs of age. Every one of God's creatures passes some day, and I've endured the loss of many great animal friends over my 63 years. Someday I'll surely join them as well.
I share your sorrow and hope that by sharing, your pain is lessened, and I echo Slings' prayer that you and Buddy are reunited at the Rainbow Bridge.
Best FRegards and God Bless.