I bought my reflectors from http://www.fiberopticproducts.com/ they charge $.25 a piece for them, so that would make Barts site a little cheaper, but you'll have to check pricing. fiber optic products ships USPS so is inexpensive.
However, as I just discovered, they don't handle heat well. Hot glue makes the chrome delaminate
As pricey as the McFloods are at $8.50 each from dat2zip's shop, given their quality they can't be beat. The McFloods are solid machined metal. (That's for Luxeons, major overkill for lesser LEDs.)