I'm going to throw a few suggestions out here:
For a slightly older Enchantress, I say Monica Bellucci. Even though she is 49, she does not look her age. She is still absolutely stunning and exotic. Here she is as a blonde (spoiler tagged in case your wife/gf is walking by...
Next, based purely on looks alone, and on the other end of the age spectrum, I would suggest Kate Upton. I have no idea whether or not she can act (in fact, I have my doubts), but I know she has been in a few films recently.
Finally, splitting the difference for the ages of my last two suggestions, is Christina Hendricks. She's worked with both Whedon and Taylor, for what that's worth. And I imagine she can pull of blonde.
Obviously I imagine a more full-bodied Enchantress than some of the other suggestions, like Alice Eve or Eva Green, but that's how I see the character.