I don't know if any of you have ever come across it, but let me recommend Pet Loss Grief Support, The Rainbow Bridge Poem, Monday Candle Ceremony
I volunteer at our local shelter, and I assure you on any given day, we have nigh onto 50 dogs or cats that are just waiting to fill the hole left in your heart. It's true that any pet leaves a hole exactly the size and shape of the pet, so no other pet will ever fill it perfectly, but I've seen so many times that it helps so much.
I'm especially reminded of a blind gentleman who came in with his daughter. His long-time cat had passed away, and, since he spends most of his time alone, he needed some company. I introduced him to a cat named "Baby," who immediately jumped into his lap, stared into his face for a few seconds, and then curled up into a purring ball. It still brings tears to my eyes...tough guy that I am...