I bought the Piping Hot Binding Tool as well, and find that using the piping foot for my machine, adjusting the needle position to make it as tight as possible to the cording while sewing, then using the piping tool to trim results in really nice piping. I use the piping foot when I sew it onto the base fabric too as it really helps with alignment.
For refills of the piping, I used drapery cording as it comes in various diameters to suit multiple purposes.
Good luck, post pics when you're done!
GEMRM

Here's a link to Nancy's Notions http://www.nancysnotions.com/product...2.2+yd+pkg+.do for fusible piping.

I bought some drapery cording at JoAnn's which was not exactly the same diameter, but very close, so it should work. Now if I can only find where I put it, I'll be ok....

The original link posted didn't work for me, but the new one above does....go figure!

You can get the exact same cording that comes with the Piping Hot Binding book at Jhittle.com.