I feel your pain, my Degu boy Edgar of 2 years got a URI and died just last week. It was devestating, he was very bonded to me and i loved the little guy. His young companion Mori was pretty restless afterwards it was hard to handle, i ended up giving him to someone who was searching for a companion for her goo.
You should definitely get a companion if you plan to keep your goo, but make sure to take your current one to the vet first to make sure he is not also sick. When i had Edgar all alone, i got Mori and introduced them and he was certainly much happier at having a companion. You just need to take things slow, especially with two boys that will fight for dominance. How i introduced mine was keeping them in separate cages that were next to each other for a week. Right away they were curious and after a week of sniffing through cages i let them say hello in a scent-neutral area (for me, the bathtub) they sniffed and warbled for a few minutes then, i separated them. These short meetings went on for another week, and gradually got a little longer. After two weeks i let them have a 'sleep over' in Edgar's cage which i had cleaned to get rid of his scent and they did just fine, they even snuggled on that very first night. I kept letting them have sleepovers, and their own space during the day, and after three weeks i permanently housed them together which seemed just fine for them. I think what really helped was that Mori was a baby when i got him (5 weeks old) so Edgar knew he had to be gentle and the two became quick buddies.
I'm sorry for your loss, hang in there and do whatever feels right. For me, i decided to give up Mori because he wasn't bonded to me at all like Edgar, in fact i'm sure he will never notice i'm gone lol he just had his own agenda. I just was so busy i hardly have any time to give him the attention he needs. The people i gave him to seemed knowledgeable of goos and their special needs they love their other one a lot so i hope i did the right thing.