I do not know of any alternative at this time -
Both Old School and Dueling with Osensei are out of print (well, actually, there are three copies of Dueling
left). I've written 2nd editions, each with five+ new chapters, and others extensively rewritten. They will be released by Freelance Academy Press in early 2014. They may release digital versions as well, but I do not know yet.
Hidden in Plain Sight is still available. There is only the book version at this time. I'm looking at IBook (with most of the other digital versions, they are either too easy to hack and in the case of Kindle, the photo reproductions are not all that good). But it's rather low on a list of projects right now.