Welcome. So sorry for your loss. As mentioned, it depends how your bird died. Was he sick? If so, it's a good idea to get your other bird vet checked before introducing a new bird. Also, when you get a new bird, you should quarantine for at least 30 days before introducing the new birds to each other. Also, keep in mind, they may not want to share a cage ever- and they shouldn't share a cage initially.
There is no guarantee your boy and a new bird would get along, just be there for your boy for the time being, if you do get another conure you will need to qt so will need another cage and you would need to introduce them to each other slowly.
You boy might be fine with another conure but at the same time they may never get along.
Welcome to the forum, and I'm so sorry for your loss, and for your lonely boys loss of his friend.
I agree with the advice others have shared, but also want to suggest that you keep a close watch on your lonely boy. I am going through a similar situation and the only lonely finch who is left, is grieving the loss of his much bigger "brother" (CAG). Despite my best efforts, the poor little guy is losing weight. He otherwise seems "happy", still singing, and flitting around his cage, but his appetite is not quite what it was.
I asked my avian vet about this, and he gave me some herbals to boost the immune system, and I'm also supplementing with a higher calorie/vitamin egg food.
Stress is hard on our feathered companions. You may want to watch for changes in appetite, and offer your lonely little guy a few extra healthy foods. Wouldn't want him to get sick while he adjusts to life without his friend.