I just did a Google search on the term "firewire 400 extension cable" and it came up with plenty of results for them so you might just want to do that too for simplicity.
A lot of them seem to be like 10' long, so keep in mind that the FW400 spec for length is a combined cable length of 15'. The 10' ones are just a couple of random links I looked at though- there are probably plenty of shorter ones available too.
Edit: I just checked Amazon and they have quite a few- the first one on
this search results page is 6', but they have three pages of results!
🙂 (Just remember that iLink, IEEE1394, IEEE1394a and FireWire 400 all describe the same thing- a 6 pin Firewire cable).
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