Brad,
I used the Sharp GP1U27X factory spec component. I bought it from one of the other readers of this board who had to buy 10 of 'em at once - I don't know what his source was (BTW, I got his last one, sorry). You might be able to round up a few people who want to go in together so you're not stuck with leftovers.

The Sharp GP1U27X fit perfectly. When you look at the PC board, you'll see a couple of tiny rectangles - these fit tiny flanges on the IR receiver.

I can't comment on the Radio Shack part...but as the website says: "The IR receiver that Radio Shack sells is not 100% reliable in this application. It may or may not work for you; most people report poor range. "

Good luck.