The bones are cable ties from Home Depot, and I like to melt the ends of them to keep them from wearing through the fabric on the stays.
There are a couple of decent articles out there on alternatives for boning. Whale bone is obviously out of the question, and I find that cable ties are a cost effective, durable, and good-looking option.
Mode Hisorique has a good one: http://www.modehistorique.com/research/boningdescriptions.pdf
Jenny LaFleur goes into some detail on the wear here: http://www.jennylafleur.com/study/boning.htm
And a really cool article I found written by an author who has tried actual baleen, and was able to compare it to other options out there. Her conclusion: reproduction baleen is not the answer: http://stay-ingalive.blogspot.com/2011/05/battle-of-boning.html
After reading these, I feel a bit better about "cheating" and using cable ties.