Firstly, I'm so sorry for you're loss, it's very hard losing a much loved pet, best friend and confidante.
I think there is no rules on when to get another dog, it's not a replacement it's a new chapter in you're lives, you'll always have the memories you shared with you're previous dog and they remain special and unique.
When Indie passed away age 12 I was utterly heartbroken, I still am 2.5 years later! I swear a part of me died with her, she meant the absolute world to me. I didn't want that heartache again, but I also didn't want to not have a dog ever again, we waited about 3 months when Charlie kinda found us! I got the opposite sex and a different colour completely, I wasn't looking to replace my beautiful girl, just to try and plug the gap she left and have joy in the house again.
Charlie is a total different personality to Indie, he's a total clown and makes us laugh every day, he's growing into a beautiful dog and I could not see myself without him ever, Indie is still and always will be a massive part of my life, i love them both unconditionally and I'm sure when you are ready you're new addition will give you as much joy and love.
You'll know when it's right x