Preferably free, of course.
I think the real answer is to somehow use the python pdf libraries. Somebody must have written this kind of converter using this library, but I haven't found it yet.
(Update, here it is. Of course, will it work with our pathetic version 2.5 python?)
http://www.xhtml2pdf.com/
Oh how interesting, they list "alternatives" to xhtml2pdf.
Here are some other options:
ImPDF seems to be the winner. It's command line, and has a free version although they are also advertising a "company license"? Needs more investigation:
http://www.tipdownload.com/ImPDF-HTML-to-PDF-Converter-Comm_103690/
The pricing page (link now lost) seemed to indicate that the command line option could only be bought under a $200 "company license", but this page seems to have a free download link:
http://www.impdf.com/html-to-pdf-cmd.htm
Here's a retail-boxed version with what's probably a trial download. Doesn't seem to have a command line though:
http://www.coolutils.com/TotalHTMLConverter
