A common phrase that is heard all over bird fairs, and pet stores, isn't the phrase that should be spoken. "My bird is so lonely. I want to get another bird to keep it company.". On occasion this is a all too true statement, but any responsible bird owner should never have to say these words. If a bird is entertained, and socialized with humans, then the bird is far from lonely. In fact in this case another bird in the house is only going to alter this bird's current relationships in a less than desirable way.
It is true that birds will always need companionship, but companionship doesn't mean apples to apples. They just need someone to pay attention to them. It is highly recommended that a bird is on a constant routine. That means feeding, cleaning and playing at the same time for about the same amount of time daily. Some birds spend the entire day with their owners while others only get an hour or two. There's pros and cons to both sides of the spectrum. Too little attention can lead to destructive behaviors (kind of like children.), but even the minimum amount of daily attention will help curb this negative effect. Spending the entire day snuggled up with your bird can cause the bird to over bond to you, and it may try to attack you to scorn you for having other mates, or more commonly become aggressive towards other people and pets in the household. This can be prevented by having others socialize with the birds through out the day too.
Naturally we can't always be with our birds, and even when possible it still is important that they have something to do. One of the key elements to a happy bird is giving them something to busy their brains. John "bird-man-iac" makes several affordibly priced bird toys that he sells at several bird fairs each year. You can catch him in march at the Tulsa, Oklahoma bird fair at the beginning of march, and at the Oklahoma city birdmart in the middle of march. He sells mostly toys for smaller parrots up to golfins cockatoos, with a few for the big beaks as well. His bathtub buddies are a favorite in the Amos flock. Especially since you can purchase several for $20.
Foraging toys can really help stimulate a bird's brain as well. Having to work through puzzles, and paper to get to treats and meals is a great way to not only give your bird something to do, but to also make sure that their beak isn't getting them into trouble.
If you feel that your bird is truly lonely, then instead of spending a few hundred dollars on a new bird. Spend it on a better cage, or toys for them. Take some more time to spend with them, and watch your bird grow to love you even more than before. A happy bird is a handled bird.