Here are some good resources for replacing the handle on any saw, but most especially smaller back saws that have a stiffener down the spine / back of the blade.
http://www.leevalley.com/
http://wenzloffandsons.com/
This family operation is only 14 miles away from me & are medium famous for their great saws.
http://www.norsewoodsmith.com/node/68
Also available as a PDF, this guy shows you how to make a complete backsaw from scratch!
http://www.norsewoodsmith.com/files/image/backsaws/pdf/Backsaw_Project.pdf
http://www.backsaw.net/cpg/
Note that the handle pictured isn't mine, just my personal favorite of all those I saw (snork) and what I aspire to.