Which ac adapter do i need for my tivo?

i have a tivo receiver and I need a replacement power cord. I do not have the original, I bought the device used without the cord. The input looks like one side is round and the other is square. On the receiver itself it says: LR114880 100-240 VAC 50/60 Hz 1A. I went to Wal-Mart and Best Buy and they don't have one, so I'm looking online and obviously I can't tell Google "one side is square and the other is round". Does anyone know what I need? Please help, I bought my Tivo 2 months ago and I still can't use it!