eSATA is really not anything like firewire and neither is HDMI.
I believe this is because ieee 1394 is a raw data interface. something like SATA really has nothing at all to do with firewire and is not compatible with it on any terms. It is purely a data/drive interface, you would have to hack it to get it to do anything else.
To get a real firewire port from something else, your only hope is parallel, cardbus, expresscard etc or something like that which you don't have.
You are left with only one capable interface, which is probably being used by your WIFI card. This is either mini PCI or mini PCI-E.
These types of adapters do exist. They are very interesting, more for experimentation or industrial embedded computing. But they will work well.
miniPCI (found on older laptops)
bwi[DOT]com/category/576 (2 different brands down the page)
They may not have it in stock, haven't seen that one for sale anywhere.
(sorry cant post urls yet)