What would be more effective than petitions is researching the product and finding out what stores retail them. Then write a thoughtful, cogent, and intelligent letter to each store expressing the concerns over the product. Keep it clean of obscenities and anything that's not totally professional. Include a list of names of people who feel the same way as an afterthought, and perhaps link to this forum and some others where discussions are raised on the issue.
Of course, this may not help stop the selling of this handbag, but it's a much better way to go about it than online petitions to the manufacturer.