Moschino's I Love Love is very similar, and I would bet there are some good deals on it online. Also Walgreens Drugstores' dupe line called InStyle has a dupe of Light Blue that I thought was pretty nice. But I Love Love would be the better bet, imo, for not much more money than the dupe.
I was going to say the same thing -- I see Light Blue on eBay and at discounters all the time. I know Loehmann's had massive stacks of it the last time I was there, and so do my local Target and CVS drugstore.