Um, it's a 7/32" nutdriver. You can probably buy them, individually or in sets, at your local big box hardware store or automotive parts store. Or basic Sears Craftsman stuff or even your local Wal-Mart. You might know a mechanic who can lend you one. No need to special order online for what is really a very basic and common tool, especially since you probably won't get anything better than what your local retailers offer without paying a premium.
I personally prefer sets with interchangable bits and socket heads, more versatile, less space, and I can always purchase single socket/bit pieces as needed in the future. Dedicated nutdrivers and screwdrivers (that is, socket/bit is permanently affixed to handle instead of being swappable) are only useful if you'll need to use that particular tool size on a frequent basis.
Most manufacturers don't advertise the clearance of the driver shaft, ie: the outer diameter of the socket head. It needs to be slim enough to fit into the recess unless you want to destroy the surrounding plastics just like that impatient loser at Deskthority. The item advertised in your eBay link doesn't specify outer diameter at all (no surprise), although it does look a little wide on the picture. Some PC computer toolkits might include the exact tool you need, since this outer-diameter problem used to be an issue back in the days when important serial and parallel ports were crowded together, although to be honest most such toolkits tend to be overpriced collections of the cheapest versions of the most redundantly useless tools you could possibly never need when fixing a PC - anyone who actually knows what they're doing inside a computer has usually assembled their own better toolkit anyhow.
Seriously, take your keyboard to your local hardware store and spend $10-20 on a complete socket set instead. It'll even accept both proper SI/Metric and silly Imperial socket heads, so you needn't bother trusting Ripster's dubious mathematical approximations. If this is one-shot job and you don't plan to disassemble this or other keyboards in the future then perhaps just use tweezers or needle nose pliers instead.
