I suggest you to try free SUPER. Although I haven't really tested it with SWF files.

What other audio/video converters that I've tested support flash .SWF files?
Moyea Flash to Video Converter can convert .swf, .exe, .flv files not only to various video formats (avi, mp4, DVD, Sony PSP, Apple iPod,...), but also to MP3 audio. In my tests it was very good.

Xilisoft video converter can convert SWF to video too, but in my tests it didn't show any decent results.

Also WinAVI video converter can convert .SWF files. Although I haven't tried it yet.

To receive the best quality instead of using audio/video converters, you may try flash decompiler (like Sothink SWF Decompiler) to extract MP3 audio track and then multiplex it with .AVI video using something like AVI Mux.