TapeTape
I've always gotten my reels from TAPETAPE.COM -- very reliable service, and both new and used tape is available. I know some thing it's heresy, but you can use one-pass tape for half the price of new and get fantastic results. I have also seen Radio Shack carrying reel-to-reel tape (I think it was 1/2"), but that was maybe three years ago and I haven't seen it since. You might want to inquire.