The Undercover Cleo series was previously published in paperback format by Berkley Books. If you look around eBay, old bookstores, or wherever, you might find one of those old copies floating around. It was also published in the Czech Republic and Slovakia, in case you really wanted a challenging eBay hunt.
But if not, don't worry. The Undercover Cleo Series is available here, as well as through various e-bookstores, like Mobipocket, Fictionwise, Diesel-ebooks, Powell's and more.
