I'm so sorry you lost your Budgie...
I agree, first thing is to make sure that your other Budgie that was housed with the one who passed-away is not also sick, as if his cagemate died from a Bacterial or Fungal infection, it's very likely that he is also sick...So I would get him to your Certified Avian Vet for cultures ASAP.
****What you DO NOT want to do is to go out and buy another bird as a friend for your male Budgie!!! There is absolutely no guarantee that whatever bird you bring home will like or bond with your current bird, or vice-versa. They may hate each other and be aggressive/violent towards each other, in which case you'd have to separate them immediately, or they may simply tolerate each other but not bond with each other, which does no good for your current bird at all...
The best thing that you can do for your male Budgie is to start working with him on a daily basis, every day, following the hand-taming steps in the links above. This is something that you have to fully commit to and not take lightly, and spend at least an hour or more a day working with him. He's only 9 months old, so it's quite possible that you can bond very closely with him and become "his person", but it will be a marathon, not a sprint, and will most-likely take months and months to accomplish. But the idea is that he already knows you and is comfortably being around you, so the best thing you can do is to try to develop a close bond with him, over time, and replace the bond he had with the female who passed away...
