I have just bought a set of these adaptors for $16 (Oz dollars) each. They seemed a tad expensive but no longer do I have to pack three different Firewire cables with me when I hit the road!
Pretty handy! I carry a single 6 pin to 4 pin, but have often wished I could go the other way around. I'll have to find a set here for me!
Or maybe I'll just wait til I'm in Melbourne
Those things are all over ebay for 99 cents (plus $4.50 s&h). 6-pin female to 4-pin male adapters, so you could have a 6-6 cable plus 2 adapters and be able to make any combination of firewire cable from it.
Haven't tried 'em, don't know if they work, just an FYI for those thinking about this solution.