The easy answer to your question is to get the Apple Wireless Keyboard at about $70. It can be combined with the Incase Origami Workstation, a keyboard case that "unfolds" into a stand to hold both the keyboard and the iPad. That combo will bring your price to about $100 total.
A good alternative is the Logitech "Tablet Keyboard for iPad" available for $70 on the Logitech.com website. A very good keyboard that comes with a keyboard case that also supports the iPad. Total of $70.
At least as good a keyboard as either of those above is the Microsoft 6000 bluetooth portable keyboard available from Amazon for less than $35. However, it's a bit larger than either of the alternatives above and cannot be combined with a keyboard case. It's best to get a separate stand if you're going to go in that direction.
Then there are the multitude of combo iPad/keyboard cases. Zagg is probably the most popular. There are innumerable knockoffs, some for sale at places like Brookstone and online from Amazon affiliated vendors.
Many people like these. I don't. The keyboards are by necessity significantly smaller than the AWK, Logitech, or Microsoft since they have to fit into a case designed for an iPad. If your brother is used to a full size keyboard, he may find the cramped keyboards of these models to be a problem, especially if he has to move back and forth between keyboards.
I'm a professional writer and bang on a keyboard for many hours each day. So I'm a bigot/picky (choose one) about good keyboards. It's no trick to make a keyboard that lasts for a few months or a year under heavy use and then breaks down. It IS a trick to make one that is truly durable. Remember that a keyboard has MANY moving parts and once a single key breaks the keyboard is useless. For those reasons, I'd recommend sticking with Apple, Logitech, or the Microsoft keyboard cited above. I've used all three brands extensively (and others much less extensively because they lacked good feel or broke) and I'd recommend sticking with a manufacturer with a good track record.