Perhaps try HelpSetMaker:
http://www.cantamen.com/helpsetmaker.php?lang=en
It's GPL and allows creating a complete HelpSet without even writing HTML (not to say TOC or HS files). You can not only create HelpSets, but also Stand-Alone HTML pages and (with the help of pdfLaTeX) PDF documents.
Best regards,
Dirk Hillbrecht
(main programmer of HelpSetMaker)
I use the expensive, but fabulous, WebWorks Publisher, since I wanted to do extensive customizations on the generated output from a single source format.
Still, there is a list of JavaHelp tools on: http://java.sun.com/products/javahelp/industry.html
As well as HelpSetMaker (already posted) here are a few (in no particular order) that I have used that are inexpensive (or free) and very good:
Helen: http://www.software7.biz/
JHelpBuilder: http://www.javio.com/jhelpbuilder/jhelpbuilder
SimplyHTML with JavaHelp Plug-in: http://www.lightdev.com/
JHelpDev: http://www.mk-home.de/
HelpBreeze HTML Help and JavaHelp Edition 3.0: http://www.solutionsoft.com/javahelp.htm
AnetHelpTool: http://www.anetsoft.com/
Take a look at all of them, since each offers slightly different features and may have a better match with your own development requirements.
All the best.