Hi Susan,
I’m sorry for your loss. If the other bird is tame and can be handled, he will be fine. But if the other bird was his only companion, then it might be best to get another one. The problem is, he may or may not accept another bird. You would need to have the new bird in a separate cage and start with the cages side by side so the bird can get used to each other. Introducing them should be gradual and under close supervision. If there are any rescue groups near you, they often get older cockatiels, so you might be able to find one to adopt.
Thank you for asking Lafeber,
Brenda