I don't see the problem with finding a Firewire cable as they are pretty standard, though I am having trouble finding references to a Canon model EOS 2D. Canon don't seem to have heard of it.
Firewire is usually a feature of digital video cameras, but the first EOS 1D had Firewire instead of USB as the early USB spec was too slow for the large image files. USB was added to later marks.
Anyway, there is a Firewire cable made by Canon on Amazon at
THIS LINK This is just one of many similar cables available. They all have a small connector at the camera end but may have a small or large connector at the computer end. Usually you want the large connector at the computer.
I believe these connectors are part of the IEEE 1394 cable spec, which varies much less than USB in sizes of connector. The picture at the site above is very good and you should be able to tell if the connector looks right for the socket on your camera. I doubt that Canon would have used some kind of proprietary connection there, but don't know for sure. When you say you are having trouble finding one, have you actually obtained one and found it didn't fit? They don't cost so much that the experiment would be expensive.
Your other problem is likely to be that most Windows PCs have a USB port, but no Firewire port. Macs often have a Firewire port but may not have USB. If your Windows PC does not have this interface, you might need to fit an add-on Firewire interface card to the computer's internal PCI bus. This will come with a driver for the card.