buy.com and amazon both have them for 42.99 with free shipping and no tax. I ordered mine through buy.com before amazon lowered their price. It came in 3 or 4 days from CA to IL. I heard that circuit city had them for 38 dollars if you can find one, but you must pay tax and NO returns.
This is the standard PS3 controller, so, yes, it will work. The controller your grandson is asking for is this same controller (but modified by an after-market company), so he's looking to cheat on the games he's playing. This is a terrible character flaw and, as his grandmother, you must correct it immediately. Tell the little scamp that "Granny doesn't like it when you pwn noobz." He'll get the message.