I agree, it shouldn't be a toy or anything. Maybe a book about being a big brother, with a note from baby on the inside cover. And a big brother tee is cute. Or get them matching teddy bears - one bigger than the other for the big brother.
I know people who get the older sibling a realistic doll with lots of the baby "stuff" so that while you care for real baby, sibling can care for their doll. I know you have a boy, but I like that idea. There are boy baby dolls out there. And a stroller, swing, bottles, diapers, etc for him to practice taking care of a baby.
(alot of dads would flip if you bought their son a doll, but I run a daycare in my home and I can tell you that the little boys like playing dolls as much as the girl like playing dinosaurs & cars!!!!)
Also, it doesn't matter if you breast or bottle feed, you'll need to think of something to keep your 2 year old busy while you feed baby. I watch a 2 yr old & her new baby sister and during bottle time is the only time the 2 year old gets to watch her favorite video. (the wiggles) It makes her not demand my (or mom's) attention during feedings and keeps her happy.
CONGRATULATIONS ON YOUR NEW ADDITION ~ ENJOY!!!!!